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12.5 String Functions

Table 12.7 String Operators

NameDescription
ASCII() Return numeric value of left-most character
BIN() Return a string containing binary representation of a number
BIT_LENGTH() Return length of argument in bits
CHAR() Return the character for each integer passed
CHAR_LENGTH() Return number of characters in argument
CHARACTER_LENGTH() Synonym for CHAR_LENGTH()
CONCAT() Return concatenated string
CONCAT_WS() Return concatenate with separator
ELT() Return string at index number
EXPORT_SET() Return a string such that for every bit set in the value bits, you get an on string and for every unset bit, you get an off string
FIELD() Return the index (position) of the first argument in the subsequent arguments
FIND_IN_SET() Return the index position of the first argument within the second argument
FORMAT() Return a number formatted to specified number of decimal places
HEX() Return a hexadecimal representation of a decimal or string value
INSERT() Insert a substring at the specified position up to the specified number of characters
INSTR() Return the index of the first occurrence of substring
LCASE() Synonym for LOWER()
LEFT() Return the leftmost number of characters as specified
LENGTH() Return the length of a string in bytes
LIKE Simple pattern matching
LOAD_FILE() Load the named file
LOCATE() Return the position of the first occurrence of substring
LOWER() Return the argument in lowercase
LPAD() Return the string argument, left-padded with the specified string
LTRIM() Remove leading spaces
MAKE_SET() Return a set of comma-separated strings that have the corresponding bit in bits set
MATCH Perform full-text search
MID() Return a substring starting from the specified position
NOT LIKE Negation of simple pattern matching
NOT REGEXP Negation of REGEXP
OCT() Return a string containing octal representation of a number
OCTET_LENGTH() Synonym for LENGTH()
ORD() Return character code for leftmost character of the argument
POSITION() Synonym for LOCATE()
QUOTE() Escape the argument for use in an SQL statement
REGEXP Pattern matching using regular expressions
REPEAT() Repeat a string the specified number of times
REPLACE() Replace occurrences of a specified string
REVERSE() Reverse the characters in a string
RIGHT() Return the specified rightmost number of characters
RLIKE Synonym for REGEXP
RPAD() Append string the specified number of times
RTRIM() Remove trailing spaces
SOUNDEX() Return a soundex string
SOUNDS LIKE Compare sounds
SPACE() Return a string of the specified number of spaces
STRCMP() Compare two strings
SUBSTR() Return the substring as specified
SUBSTRING() Return the substring as specified
SUBSTRING_INDEX() Return a substring from a string before the specified number of occurrences of the delimiter
TRIM() Remove leading and trailing spaces
UCASE() Synonym for UPPER()
UNHEX() Return a string containing hex representation of a number
UPPER() Convert to uppercase

String-valued functions return NULL if the length of the result would be greater than the value of the max_allowed_packet system variable. See Section 8.12.2, “Tuning Server Parameters”.

For functions that operate on string positions, the first position is numbered 1.

For functions that take length arguments, noninteger arguments are rounded to the nearest integer.

  • ASCII(str)

    Returns the numeric value of the leftmost character of the string str. Returns 0 if str is the empty string. Returns NULL if str is NULL. ASCII() works for 8-bit characters.

    mysql> SELECT ASCII('2');
            -> 50
    mysql> SELECT ASCII(2);
            -> 50
    mysql> SELECT ASCII('dx');
            -> 100
    

    See also the ORD() function.

  • BIN(N)

    Returns a string representation of the binary value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,2). Returns NULL if N is NULL.

    mysql> SELECT BIN(12);
            -> '1100'
    
  • BIT_LENGTH(str)

    Returns the length of the string str in bits.

    mysql> SELECT BIT_LENGTH('text');
            -> 32
    
  • CHAR(N,... [USING charset_name])

    CHAR() interprets each argument N as an integer and returns a string consisting of the characters given by the code values of those integers. NULL values are skipped.

    mysql> SELECT CHAR(77,121,83,81,'76');
            -> 'MySQL'
    mysql> SELECT CHAR(77,77.3,'77.3');
            -> 'MMM'
    

    CHAR() arguments larger than 255 are converted into multiple result bytes. For example, CHAR(256) is equivalent to CHAR(1,0), and CHAR(256*256) is equivalent to CHAR(1,0,0):

    mysql> SELECT HEX(CHAR(1,0)), HEX(CHAR(256));
    +----------------+----------------+
    | HEX(CHAR(1,0)) | HEX(CHAR(256)) |
    +----------------+----------------+
    | 0100           | 0100           |
    +----------------+----------------+
    mysql> SELECT HEX(CHAR(1,0,0)), HEX(CHAR(256*256));
    +------------------+--------------------+
    | HEX(CHAR(1,0,0)) | HEX(CHAR(256*256)) |
    +------------------+--------------------+
    | 010000           | 010000             |
    +------------------+--------------------+
    

    By default, CHAR() returns a binary string. To produce a string in a given character set, use the optional USING clause:

    mysql> SELECT CHARSET(CHAR(X'65')), CHARSET(CHAR(X'65' USING utf8));
    +----------------------+---------------------------------+
    | CHARSET(CHAR(X'65')) | CHARSET(CHAR(X'65' USING utf8)) |
    +----------------------+---------------------------------+
    | binary               | utf8                            |
    +----------------------+---------------------------------+
    

    If USING is given and the result string is illegal for the given character set, a warning is issued. Also, if strict SQL mode is enabled, the result from CHAR() becomes NULL.

  • CHAR_LENGTH(str)

    Returns the length of the string str, measured in characters. A multibyte character counts as a single character. This means that for a string containing five 2-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.

  • CHARACTER_LENGTH(str)

    CHARACTER_LENGTH() is a synonym for CHAR_LENGTH().

  • CONCAT(str1,str2,...)

    Returns the string that results from concatenating the arguments. May have one or more arguments. If all arguments are nonbinary strings, the result is a nonbinary string. If the arguments include any binary strings, the result is a binary string. A numeric argument is converted to its equivalent string form. This is a nonbinary string as of MySQL 5.5.3. Before 5.5.3, it is a binary string; to avoid that and produce a nonbinary string, you can use an explicit type cast, as in this example:

    SELECT CONCAT(CAST(int_col AS CHAR), char_col);
    

    CONCAT() returns NULL if any argument is NULL.

    mysql> SELECT CONCAT('My', 'S', 'QL');
            -> 'MySQL'
    mysql> SELECT CONCAT('My', NULL, 'QL');
            -> NULL
    mysql> SELECT CONCAT(14.3);
            -> '14.3'
    

    For quoted strings, concatenation can be performed by placing the strings next to each other:

    mysql> SELECT 'My' 'S' 'QL';
            -> 'MySQL'
    
  • CONCAT_WS(separator,str1,str2,...)

    CONCAT_WS() stands for Concatenate With Separator and is a special form of CONCAT(). The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL.

    mysql> SELECT CONCAT_WS(',','First name','Second name','Last Name');
            -> 'First name,Second name,Last Name'
    mysql> SELECT CONCAT_WS(',','First name',NULL,'Last Name');
            -> 'First name,Last Name'
    

    CONCAT_WS() does not skip empty strings. However, it does skip any NULL values after the separator argument.

  • ELT(N,str1,str2,str3,...)

    ELT() returns the Nth element of the list of strings: str1 if N = 1, str2 if N = 2, and so on. Returns NULL if N is less than 1 or greater than the number of arguments. ELT() is the complement of FIELD().

    mysql> SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo');
            -> 'ej'
    mysql> SELECT ELT(4, 'ej', 'Heja', 'hej', 'foo');
            -> 'foo'
    
  • EXPORT_SET(bits,on,off[,separator[,number_of_bits]])

    Returns a string such that for every bit set in the value bits, you get an on string and for every bit not set in the value, you get an off string. Bits in bits are examined from right to left (from low-order to high-order bits). Strings are added to the result from left to right, separated by the separator string (the default being the comma character ,). The number of bits examined is given by number_of_bits, which has a default of 64 if not specified. number_of_bits is silently clipped to 64 if larger than 64. It is treated as an unsigned integer, so a value of −1 is effectively the same as 64.

    mysql> SELECT EXPORT_SET(5,'Y','N',',',4);
            -> 'Y,N,Y,N'
    mysql> SELECT EXPORT_SET(6,'1','0',',',10);
            -> '0,1,1,0,0,0,0,0,0,0'
    
  • FIELD(str,str1,str2,str3,...)

    Returns the index (position) of str in the str1, str2, str3, ... list. Returns 0 if str is not found.

    If all arguments to FIELD() are strings, all arguments are compared as strings. If all arguments are numbers, they are compared as numbers. Otherwise, the arguments are compared as double.

    If str is NULL, the return value is 0 because NULL fails equality comparison with any value. FIELD() is the complement of ELT().

    mysql> SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo');
            -> 2
    mysql> SELECT FIELD('fo', 'Hej', 'ej', 'Heja', 'hej', 'foo');
            -> 0
    
  • FIND_IN_SET(str,strlist)

    Returns a value in the range of 1 to N if the string str is in the string list strlist consisting of N substrings. A string list is a string composed of substrings separated by , characters. If the first argument is a constant string and the second is a column of type SET, the FIND_IN_SET() function is optimized to use bit arithmetic. Returns 0 if str is not in strlist or if strlist is the empty string. Returns NULL if either argument is NULL. This function does not work properly if the first argument contains a comma (,) character.

    mysql> SELECT FIND_IN_SET('b','a,b,c,d');
            -> 2
    
  • FORMAT(X,D[,locale])

    Formats the number X to a format like '#,###,###.##', rounded to D decimal places, and returns the result as a string. If D is 0, the result has no decimal point or fractional part.

    The optional third parameter enables a locale to be specified to be used for the result number's decimal point, thousands separator, and grouping between separators. Permissible locale values are the same as the legal values for the lc_time_names system variable (see Section 10.7, “MySQL Server Locale Support”). If no locale is specified, the default is 'en_US'.

    mysql> SELECT FORMAT(12332.123456, 4);
            -> '12,332.1235'
    mysql> SELECT FORMAT(12332.1,4);
            -> '12,332.1000'
    mysql> SELECT FORMAT(12332.2,0);
            -> '12,332'
    mysql> SELECT FORMAT(12332.2,2,'de_DE');
            -> '12.332,20'
    
  • HEX(str), HEX(N)

    For a string argument str, HEX() returns a hexadecimal string representation of str where each byte of each character in str is converted to two hexadecimal digits. (Multibyte characters therefore become more than two digits.) The inverse of this operation is performed by the UNHEX() function.

    For a numeric argument N, HEX() returns a hexadecimal string representation of the value of N treated as a longlong (BIGINT) number. This is equivalent to CONV(N,10,16). The inverse of this operation is performed by CONV(HEX(N),16,10).

    mysql> SELECT X'616263', HEX('abc'), UNHEX(HEX('abc'));
            -> 'abc', 616263, 'abc'
    mysql> SELECT HEX(255), CONV(HEX(255),16,10);
            -> 'FF', 255
    
  • INSERT(str,pos,len,newstr)

    Returns the string str, with the substring beginning at position pos and len characters long replaced by the string newstr. Returns the original string if pos is not within the length of the string. Replaces the rest of the string from position pos if len is not within the length of the rest of the string. Returns NULL if any argument is NULL.

    mysql> SELECT INSERT('Quadratic', 3, 4, 'What');
            -> 'QuWhattic'
    mysql> SELECT INSERT('Quadratic', -1, 4, 'What');
            -> 'Quadratic'
    mysql> SELECT INSERT('Quadratic', 3, 100, 'What');
            -> 'QuWhat'
    

    This function is multibyte safe.

  • INSTR(str,substr)

    Returns the position of the first occurrence of substring substr in string str. This is the same as the two-argument form of LOCATE(), except that the order of the arguments is reversed.

    mysql> SELECT INSTR('foobarbar', 'bar');
            -> 4
    mysql> SELECT INSTR('xbar', 'foobar');
            -> 0
    

    This function is multibyte safe, and is case sensitive only if at least one argument is a binary string.

  • LCASE(str)

    LCASE() is a synonym for LOWER().

  • LEFT(str,len)

    Returns the leftmost len characters from the string str, or NULL if any argument is NULL.

    mysql> SELECT LEFT('foobarbar', 5);
            -> 'fooba'
    

    This function is multibyte safe.

  • LENGTH(str)

    Returns the length of the string str, measured in bytes. A multibyte character counts as multiple bytes. This means that for a string containing five 2-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.

    mysql> SELECT LENGTH('text');
            -> 4
    
    Note

    The Length() OpenGIS spatial function is named GLength() in MySQL.

  • LOAD_FILE(file_name)

    Reads the file and returns the file contents as a string. To use this function, the file must be located on the server host, you must specify the full path name to the file, and you must have the FILE privilege. The file must be readable by all and its size less than max_allowed_packet bytes. If the secure_file_priv system variable is set to a nonempty directory name, the file to be loaded must be located in that directory.

    If the file does not exist or cannot be read because one of the preceding conditions is not satisfied, the function returns NULL.

    The character_set_filesystem system variable controls interpretation of file names that are given as literal strings.

    mysql> UPDATE t
                SET blob_col=LOAD_FILE('/tmp/picture')
                WHERE id=1;
    
  • LOCATE(substr,str), LOCATE(substr,str,pos)

    The first syntax returns the position of the first occurrence of substring substr in string str. The second syntax returns the position of the first occurrence of substring substr in string str, starting at position pos. Returns 0 if substr is not in str.

    mysql> SELECT LOCATE('bar', 'foobarbar');
            -> 4
    mysql> SELECT LOCATE('xbar', 'foobar');
            -> 0
    mysql> SELECT LOCATE('bar', 'foobarbar', 5);
            -> 7
    

    This function is multibyte safe, and is case-sensitive only if at least one argument is a binary string.

  • LOWER(str)

    Returns the string str with all characters changed to lowercase according to the current character set mapping. The default is latin1 (cp1252 West European).

    mysql> SELECT LOWER('QUADRATICALLY');
            -> 'quadratically'
    

    LOWER() (and UPPER()) are ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). To perform lettercase conversion, convert the string to a nonbinary string:

    mysql> SET @str = BINARY 'New York';
    mysql> SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
    +-------------+-----------------------------------+
    | LOWER(@str) | LOWER(CONVERT(@str USING latin1)) |
    +-------------+-----------------------------------+
    | New York    | new york                          |
    +-------------+-----------------------------------+
    

    This function is multibyte safe.

  • LPAD(str,len,padstr)

    Returns the string str, left-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters.

    mysql> SELECT LPAD('hi',4,'??');
            -> '??hi'
    mysql> SELECT LPAD('hi',1,'??');
            -> 'h'
    
  • LTRIM(str)

    Returns the string str with leading space characters removed.

    mysql> SELECT LTRIM('  barbar');
            -> 'barbar'
    

    This function is multibyte safe.

  • MAKE_SET(bits,str1,str2,...)

    Returns a set value (a string containing substrings separated by , characters) consisting of the strings that have the corresponding bit in bits set. str1 corresponds to bit 0, str2 to bit 1, and so on. NULL values in str1, str2, ... are not appended to the result.

    mysql> SELECT MAKE_SET(1,'a','b','c');
            -> 'a'
    mysql> SELECT MAKE_SET(1 | 4,'hello','nice','world');
            -> 'hello,world'
    mysql> SELECT MAKE_SET(1 | 4,'hello','nice',NULL,'world');
            -> 'hello'
    mysql> SELECT MAKE_SET(0,'a','b','c');
            -> ''
    
  • MID(str,pos,len)

    MID(str,pos,len) is a synonym for SUBSTRING(str,pos,len).

  • OCT(N)

    Returns a string representation of the octal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,8). Returns NULL if N is NULL.

    mysql> SELECT OCT(12);
            -> '14'
    
  • OCTET_LENGTH(str)

    OCTET_LENGTH() is a synonym for LENGTH().

  • ORD(str)

    If the leftmost character of the string str is a multibyte character, returns the code for that character, calculated from the numeric values of its constituent bytes using this formula:

      (1st byte code)
    + (2nd byte code * 256)
    + (3rd byte code * 2562) ...
    

    If the leftmost character is not a multibyte character, ORD() returns the same value as the ASCII() function.

    mysql> SELECT ORD('2');
            -> 50
    
  • POSITION(substr IN str)

    POSITION(substr IN str) is a synonym for LOCATE(substr,str).

  • QUOTE(str)

    Quotes a string to produce a result that can be used as a properly escaped data value in an SQL statement. The string is returned enclosed by single quotation marks and with each instance of backslash (\), single quote ('), ASCII NUL, and Control+Z preceded by a backslash. If the argument is NULL, the return value is the word NULL without enclosing single quotation marks.

    mysql> SELECT QUOTE('Don\'t!');
            -> 'Don\'t!'
    mysql> SELECT QUOTE(NULL);
            -> NULL
    

    For comparison, see the quoting rules for literal strings and within the C API in Section 9.1.1, “String Literals”, and Section 23.8.7.53, “mysql_real_escape_string()”.

  • REPEAT(str,count)

    Returns a string consisting of the string str repeated count times. If count is less than 1, returns an empty string. Returns NULL if str or count are NULL.

    mysql> SELECT REPEAT('MySQL', 3);
            -> 'MySQLMySQLMySQL'
    
  • REPLACE(str,from_str,to_str)

    Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str.

    mysql> SELECT REPLACE('www.mysql.com', 'w', 'Ww');
            -> 'WwWwWw.mysql.com'
    

    This function is multibyte safe.

  • REVERSE(str)

    Returns the string str with the order of the characters reversed.

    mysql> SELECT REVERSE('abc');
            -> 'cba'
    

    This function is multibyte safe.

  • RIGHT(str,len)

    Returns the rightmost len characters from the string str, or NULL if any argument is NULL.

    mysql> SELECT RIGHT('foobarbar', 4);
            -> 'rbar'
    

    This function is multibyte safe.

  • RPAD(str,len,padstr)

    Returns the string str, right-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters.

    mysql> SELECT RPAD('hi',5,'?');
            -> 'hi???'
    mysql> SELECT RPAD('hi',1,'?');
            -> 'h'
    

    This function is multibyte safe.

  • RTRIM(str)

    Returns the string str with trailing space characters removed.

    mysql> SELECT RTRIM('barbar   ');
            -> 'barbar'
    

    This function is multibyte safe.

  • SOUNDEX(str)

    Returns a soundex string from str. Two strings that sound almost the same should have identical soundex strings. A standard soundex string is four characters long, but the SOUNDEX() function returns an arbitrarily long string. You can use SUBSTRING() on the result to get a standard soundex string. All nonalphabetic characters in str are ignored. All international alphabetic characters outside the A-Z range are treated as vowels.

    Important

    When using SOUNDEX(), you should be aware of the following limitations:

    • This function, as currently implemented, is intended to work well with strings that are in the English language only. Strings in other languages may not produce reliable results.

    • This function is not guaranteed to provide consistent results with strings that use multibyte character sets, including utf-8.

      We hope to remove these limitations in a future release. See Bug #22638 for more information.

    mysql> SELECT SOUNDEX('Hello');
            -> 'H400'
    mysql> SELECT SOUNDEX('Quadratically');
            -> 'Q36324'
    
    Note

    This function implements the original Soundex algorithm, not the more popular enhanced version (also described by D. Knuth). The difference is that original version discards vowels first and duplicates second, whereas the enhanced version discards duplicates first and vowels second.

  • expr1 SOUNDS LIKE expr2

    This is the same as SOUNDEX(expr1) = SOUNDEX(expr2).

  • SPACE(N)

    Returns a string consisting of N space characters.

    mysql> SELECT SPACE(6);
            -> '      '
    
  • SUBSTR(str,pos), SUBSTR(str FROM pos), SUBSTR(str,pos,len), SUBSTR(str FROM pos FOR len)

    SUBSTR() is a synonym for SUBSTRING().

  • SUBSTRING(str,pos), SUBSTRING(str FROM pos), SUBSTRING(str,pos,len), SUBSTRING(str FROM pos FOR len)

    The forms without a len argument return a substring from string str starting at position pos. The forms with a len argument return a substring len characters long from string str, starting at position pos. The forms that use FROM are standard SQL syntax. It is also possible to use a negative value for pos. In this case, the beginning of the substring is pos characters from the end of the string, rather than the beginning. A negative value may be used for pos in any of the forms of this function.

    For all forms of SUBSTRING(), the position of the first character in the string from which the substring is to be extracted is reckoned as 1.

    mysql> SELECT SUBSTRING('Quadratically',5);
            -> 'ratically'
    mysql> SELECT SUBSTRING('foobarbar' FROM 4);
            -> 'barbar'
    mysql> SELECT SUBSTRING('Quadratically',5,6);
            -> 'ratica'
    mysql> SELECT SUBSTRING('Sakila', -3);
            -> 'ila'
    mysql> SELECT SUBSTRING('Sakila', -5, 3);
            -> 'aki'
    mysql> SELECT SUBSTRING('Sakila' FROM -4 FOR 2);
            -> 'ki'
    

    This function is multibyte safe.

    If len is less than 1, the result is the empty string.

  • SUBSTRING_INDEX(str,delim,count)

    Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim.

    mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', 2);
            -> 'www.mysql'
    mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', -2);
            -> 'mysql.com'
    

    This function is multibyte safe.

  • TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str)

    Returns the string str with all remstr prefixes or suffixes removed. If none of the specifiers BOTH, LEADING, or TRAILING is given, BOTH is assumed. remstr is optional and, if not specified, spaces are removed.

    mysql> SELECT TRIM('  bar   ');
            -> 'bar'
    mysql> SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
            -> 'barxxx'
    mysql> SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
            -> 'bar'
    mysql> SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
            -> 'barx'
    

    This function is multibyte safe.

  • UCASE(str)

    UCASE() is a synonym for UPPER().

  • UNHEX(str)

    For a string argument str, UNHEX(str) interprets each pair of characters in the argument as a hexadecimal number and converts it to the byte represented by the number. The return value is a binary string.

    mysql> SELECT UNHEX('4D7953514C');
            -> 'MySQL'
    mysql> SELECT X'4D7953514C';
            -> 'MySQL'
    mysql> SELECT UNHEX(HEX('string'));
            -> 'string'
    mysql> SELECT HEX(UNHEX('1267'));
            -> '1267'
    

    The characters in the argument string must be legal hexadecimal digits: '0' .. '9', 'A' .. 'F', 'a' .. 'f'. If the argument contains any nonhexadecimal digits, the result is NULL:

    mysql> SELECT UNHEX('GG');
    +-------------+
    | UNHEX('GG') |
    +-------------+
    | NULL        |
    +-------------+
    

    A NULL result can occur if the argument to UNHEX() is a BINARY column, because values are padded with 0x00 bytes when stored but those bytes are not stripped on retrieval. For example, '41' is stored into a CHAR(3) column as '41 ' and retrieved as '41' (with the trailing pad space stripped), so UNHEX() for the column value returns 'A'. By contrast '41' is stored into a BINARY(3) column as '41\0' and retrieved as '41\0' (with the trailing pad 0x00 byte not stripped). '\0' is not a legal hexadecimal digit, so UNHEX() for the column value returns NULL.

    For a numeric argument N, the inverse of HEX(N) is not performed by UNHEX(). Use CONV(HEX(N),16,10) instead. See the description of HEX().

  • UPPER(str)

    Returns the string str with all characters changed to uppercase according to the current character set mapping. The default is latin1 (cp1252 West European).

    mysql> SELECT UPPER('Hej');
            -> 'HEJ'
    

    See the description of LOWER() for information that also applies to UPPER(), such as information about how to perform lettercase conversion of binary strings (BINARY, VARBINARY, BLOB) for which these functions are ineffective.

    This function is multibyte safe.


User Comments
  Posted by Noam Rathaus on March 15, 2006
The following ORDER BY will sort a column called Host (varchar 255) that contains either a Hostname or IP addresses, whenever the IP address is found it will be sorted not as string but as integers:

ORDER BY
CAST(SUBSTRING(
Host,
1,
LOCATE('.', Host) - 1)
AS UNSIGNED),
CAST(SUBSTRING(
Host,
LOCATE('.', Host) + 1,
LOCATE('.', Host, LOCATE('.', Host) + 1)
- LOCATE('.', Host) - 1)
AS UNSIGNED),
CAST(SUBSTRING(
Host,
LOCATE('.', Host, LOCATE('.', Host) + 1) + 1,
LOCATE('.', Host,
LOCATE('.', Host, LOCATE('.', Host) + 1) + 1)
- LOCATE('.', Host, LOCATE('.', Host) + 1) - 1)
AS UNSIGNED),
CAST(SUBSTRING(
Host,
LOCATE('.', Host, LOCATE('.', Host,
LOCATE('.', Host) + 1) + 1) + 1,
3)
AS UNSIGNED)

  Posted by Bob Collins on March 17, 2006
MySQL does not include a function to split a delimited string. Although separated data would normally be split into separate fields within a relation data, spliting such can be useful either during initial data load/validation or where such data is held in a text field.

The following formula can be used to extract the Nth item in a delimited list, in this case the 3rd item "ccccc" in the example comma separated list.

select replace(substring(substring_index('aaa,bbbb,ccccc', ',', 3), length(substring_index('aaa,bbbb,ccccc', ',', 3 - 1)) + 1), ',', '') ITEM3

The above formula does not need the first item to be handled as a special case and returns empty strings correctly when the item count is less than the position requested.

More on this and related matters can be found at http://www.kanolife.com/escape/2006/03/mysql-string-splitter.html
  Posted by on March 22, 2006
This will split an IP address ("a.b.c.d") into 4 respective octets:

SELECT
`ip` ,
SUBSTRING_INDEX( `ip` , '.', 1 ) AS a,
SUBSTRING_INDEX(SUBSTRING_INDEX( `ip` , '.', 2 ),'.',-1) AS b,
SUBSTRING_INDEX(SUBSTRING_INDEX( `ip` , '.', -2 ),'.',1) AS c,
SUBSTRING_INDEX( `ip` , '.', -1 ) AS d
FROM log_table

  Posted by on March 31, 2006
I found myself wanting a unique list of domain names from a table/column of fully qualified email addresses. There isn't a split function so using the other comments here I've devised this:

SELECT DISTINCT REVERSE(LEFT(REVERSE(email),LOCATE('@',REVERSE(email)) - 1)) AS domain FROM table ORDER BY domain

Reverses email, counts the characters from left minus the @. Reverses the reverse and returns 'domain.com'.

Perhaps there is a better/fast/easier way, however it's not easily found. So here is mine.

  Posted by Dan Nelson on April 6, 2006
[name withheld], you could extract the domain in two simpler ways:

SELECT SUBSTRING_INDEX(email,'@',-1) AS domain FROM TABLE -- returns everything to the right of the rightmost @

SELECT SUBSTRING(email,INSTR(email,'@')+1) AS domain FROM TABLE -- returns everything to the right of the leftmost @

Both will return identical results on email addresses, since they only have one @ in them. I can't believe you didn't think of SUBSTRING_INDEX, even after the previous two comments used it :)

  Posted by Tom O'Malley on April 17, 2006
An example of how to make the first letter in a string uppercase - analogous to UCFIRST

SELECT CONCAT(UPPER(SUBSTRING(firstName, 1, 1)), LOWER(SUBSTRING(firstName FROM 2))) AS properFirstName
  Posted by Martin Krsek on May 16, 2006
CONCAT_WS(' AND ', NULL, NULL)
returns empty string instead of NULL, so

SET @where_cond = CONCAT_WS(' AND ', @where1, @where2);
SET @sql = CONCAT_WS(' WHERE ', 'SELECT * FROM table', @where_cond);
SELECT @sql;
results in
SELECT * FROM table WHERE
if both @where1 and @where2 are NULL
  Posted by on May 20, 2006
For folks trying to lookup Countries associated with IPs (as in, e.g., databases found here: http://ip-to-country.webhosting.info/node/view/6), this should do the trick, building on an earlier contribution to this page (Assumes your IP is called "RemoteAddress"):

select RemoteAddress as IP,
( SUBSTRING_INDEX( RemoteAddress, '.', 1 ) * 16777216 +
SUBSTRING_INDEX(SUBSTRING_INDEX( RemoteAddress, '.', 2 ),'.',-1) * 65536 +
SUBSTRING_INDEX(SUBSTRING_INDEX( RemoteAddress, '.', -2 ),'.',1) * 256 +
SUBSTRING_INDEX( RemoteAddress, '.', -1 )
) AS IP2Num
FROM log
;

  Posted by Erel Segal on July 24, 2006
Here is a trick to create a simple horizontal graph:

SELECT ColName, EXPORT_SET(pow(2,round(ColName))-1,'+','-','',70) FROM TableName

This will create an area filled with "+", where the length of each "+" bar equals the number in column ColName in that row.

70 is an upper bound on the values in ColName; change it to match your actual data.
  Posted by Erel Segal on July 24, 2006
Correction to the previous tip: in the current version, EXPORT_SET does not create a string with more than 64 chars, even if you explicitly ask for 70 chars.

Another problem is that for numbers N > 53, 2^N - 1 equals 2^N because of rounding errors, so you will not see a bar, only a single "+".
  Posted by Andrew Hanna on August 24, 2006
I created a user-defined function in MySQL 5.0+ similar to PHP's substr_count(), since I could not find an equivalent native function in MySQL. (If there is one please tell me!!!)

delimiter ||
DROP FUNCTION IF EXISTS substrCount||
CREATE FUNCTION substrCount(s VARCHAR(255), ss VARCHAR(255)) RETURNS TINYINT(3) UNSIGNED LANGUAGE SQL NOT DETERMINISTIC READS SQL DATA
BEGIN
DECLARE count TINYINT(3) UNSIGNED;
DECLARE offset TINYINT(3) UNSIGNED;
DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET s = NULL;

SET count = 0;
SET offset = 1;

REPEAT
IF NOT ISNULL(s) AND offset > 0 THEN
SET offset = LOCATE(ss, s, offset);
IF offset > 0 THEN
SET count = count + 1;
SET offset = offset + 1;
END IF;
END IF;
UNTIL ISNULL(s) OR offset = 0 END REPEAT;

RETURN count;
END;
||
delimiter ;

Use like this:

SELECT substrCount('/this/is/a/path', '/') `count`;

`count` would return 4 in this case. Can be used in such cases where you might want to find the "depth" of a path, or for many other uses.
  Posted by Michael Newton on August 31, 2006
To [name withheld] who suggested a method for turning IP addresses into numbers, I would suggest that the INET_ATON() function is a little easier to use!
  Posted by NOT_FOUND NOT_FOUND on August 21, 2008
It's pretty easy to create your own string functions for many examples listed here

## Count substrings

CREATE FUNCTION substrCount(x varchar(255), delim varchar(12)) returns int
return (length(x)-length(REPLACE(x, delim, '')))/length(delim);

SELECT substrCount('/this/is/a/path', '/') as count;
+-------+
| count |
+-------+
| 4 |
+-------+

SELECT substrCount('/this/is/a/path', 'is') as count;
+-------+
| count |
+-------+
| 2 |
+-------+

## Split delimited strings

CREATE FUNCTION strSplit(x varchar(255), delim varchar(12), pos int) returns varchar(255)
return replace(substring(substring_index(x, delim, pos), length(substring_index(x, delim, pos - 1)) + 1), delim, '');

select strSplit("aaa,b,cc,d", ',', 2) as second;
+--------+
| second |
+--------+
| b |
+--------+

select strSplit("a|bb|ccc|dd", '|', 3) as third;
+-------+
| third |
+-------+
| ccc |
+-------+

select strSplit("aaa,b,cc,d", ',', 7) as 7th;
+------+
| 7th |
+------+
| NULL |
+------+

## Upper case first letter, UCFIRST or INITCAP

CREATE FUNCTION ucfirst(x varchar(255)) returns varchar(255)
return concat( upper(substring(x,1,1)),lower(substring(x,2)) );

select ucfirst("TEST");

+-----------------+
| ucfirst("TEST") |
+-----------------+
| Test |
+-----------------+

##Or a more complicated example, this will repeat an insert after every nth position.

drop function insert2;
DELIMITER //
CREATE FUNCTION insert2(str text, pos int, delimit varchar(124))
RETURNS text
DETERMINISTIC
BEGIN
DECLARE i INT DEFAULT 1;
DECLARE str_len INT;
DECLARE out_str text default '';
SET str_len=length(str);
WHILE(i<str_len) DO
SET out_str=CONCAT(out_str, SUBSTR(str, i,pos), delimit);
SET i=i+pos;
END WHILE;
-- trim delimiter from end of string
SET out_str=TRIM(trailing delimit from out_str);
RETURN(out_str);
END//
DELIMITER ;

select insert2("ATGCATACAGTTATTTGA", 3, " ") as seq2;
+-------------------------+
| seq2 |
+-------------------------+
| ATG CAT ACA GTT ATT TGA |
+-------------------------+

  Posted by w pociengel on October 20, 2006
I was trying to output a text message that told me if a field was null. I tried various mechanisms but this proved to do the trick.

elt(((field1 <=> NULL) + 1),"not null", "null")

evaluating (field1 <=> NULL) returns 0 (zero) if the field is not null and 1 (one) if the field is null. Adding 1 (one) to this result provides positional information that fits what 'elt' expects.

elt will return "not null" (position 1) if the evaluation of ((field1 <=> NULL) + 1) = 1

it will return "null" (position 2) if the evaluation of ((field1 <=> NULL) + 1) = 2

This can be altered to output messages based on any test that I've tried. Just remember that 'elt' returns null or 1 for a comparison so you need to add 1 (one) to that result to be able to choose between different messages.
  Posted by J Vera on October 26, 2006
As above I couldn't find a function for splitting strings based on a character set rather than string position, where the results were independent of substring lengths. I used this query to split out the Swiss-Prot accession numbers from BLAST result subject ID's, which are bracketed by pipe ('|') characters, but any two relatively unique characters should work.

select left(substring(<columnName>,locate('|',<columnName>)+1),
locate('|',substring(<columnName>,
locate('|',<columnName>)+1))-1)
as '<resultColumnName>' from <table>
  Posted by Giovanni Campagnoli on December 20, 2006
This is the php function strip_tags

delimiter ||

DROP FUNCTION IF EXISTS strip_tags||
CREATE FUNCTION strip_tags( x longtext) RETURNS longtext
LANGUAGE SQL NOT DETERMINISTIC READS SQL DATA
BEGIN
DECLARE sstart INT UNSIGNED;
DECLARE ends INT UNSIGNED;
SET sstart = LOCATE('<', x, 1);
REPEAT
SET ends = LOCATE('>', x, sstart);
SET x = CONCAT(SUBSTRING( x, 1 ,sstart -1) ,SUBSTRING(x, ends +1 )) ;
SET sstart = LOCATE('<', x, 1);
UNTIL sstart < 1 END REPEAT;
return x;
END;
||
delimiter ;

mysql> SELECT strip_tags('<a href="HelloWorld.html"><B>Hi, mate!</B></a>') as strip_tags;
+------------+
| strip_tags |
+------------+
| Hi, mate! |
+------------+
1 row in set (0.00 sec)

  Posted by Stephen Gornick on December 24, 2006
If using statement-based replication, load_file() will fail on the slave unless the same file exists on the slave as on the master.
  Posted by Nicola De Franceschi on January 16, 2007
Here's my formula to remove a value from a string field of comma separated values. You can use a different delimiter just repalce the comma in the formula but pay attention since lot of commas here are the argument separator of the used functions.
The nice part is that with this formula you don't need to distinguish the first and last element of the string and this formula removes just the value_to_remove so if your initial string is: "4,11,34" and the value you want to remove is "4" you'll get "11,34".

UPDATE temp SET string = TRIM(BOTH ',' FROM REPLACE(CONCAT("," , string, ","), CONCAT(",",'value_to_remove', ",") , ',')) WHERE id=1
  Posted by Robert Glover on February 13, 2007
There is a simple way to convert the following Oracle usage of decode into MySql:

Oracle version:

select BU, count(line_number) total,
sum(decode(RECERTIFY_FLAG,'Y',1,0)) needed,
sum(decode(RECERTIFY_FLAG,'N',1,0)) not_needed,
sum(decode(RECERTIFY_FLAG,'Y',0,'N',0,1)) not_processed
from isf.isf_analog_line group by bu order by bu

MySql version that gives same results:

select BU, count(line_number) total,
sum(FIND_IN_SET(RECERTIFY_FLAG,'Y')) needed,
sum(FIND_IN_SET(RECERTIFY_FLAG,'N')) not_needed,
sum(FIND_IN_SET(RECERTIFY_FLAG,' ')) not_processed
from isf.isf_analog_line group by bu order by bu

Add your own comment.
  Posted by Balaji Devarajan on March 8, 2007
I was looking for word_count("string") in mysql, finally came up with an user defined function which is very usefull for me, note: I used <space> for actual space.
DROP FUNCTION IF EXISTS word_count;
CREATE FUNCTION word_count (f_string text(5000)) RETURNS smallint(10)
BEGIN
DECLARE new_string text(5000);
WHILE INSTR(f_string,'<space><space>')>0
DO
SET new_string=(select REPLACE(f_string,'<space><space>','<space>'));
SET f_string=new_string;
END WHILE;

RETURN (select LENGTH(TRIM(f_string))-LENGTH(REPLACE(TRIM(f_string),'<space>',''))+1);
END
//
Here is the result
mysql> select word_count("<space>Balaji<space><space><space> Devarajan<space>") WORD_COUNT;
+------------+
| WORD_COUNT |
+------------+
| 2 |
+------------+
1 row in set (0.00 sec)
mysql> select word_count(" Balaji Devarajan ") WORD_COUNT;
+------------+
| WORD_COUNT |
+------------+
| 2 |
+------------+
1 row in set (0.00 sec)
mysql> select word_count("Balaji Devarajan") WORD_COUNT;
+------------+
| WORD_COUNT |
+------------+
| 2 |
+------------+
1 row in set (0.01 sec)
  Posted by Balaji Devarajan on March 8, 2007
Here is another function I wrote, which is very usefull in getting the domain name from the url, please bare with the spaces in the http : //, if not iam not able to submit this with many urls
delimiter //
drop function if exists sub_domain;
CREATE FUNCTION sub_domain (url text(1000)) RETURNS CHAR(50)
BEGIN
DECLARE str1 varchar(10);
DECLARE str2 varchar(10);
SET str1=http : //;
SET str2=https://;
RETURN if(substring_index(substring_index(substring_index(REPLACE(url,str2,str1), '/',3),str1,-1),'.',-1) != 'com',substring_index(substring_index(substring_index(REPLACE(url,str2,str1), '/',3),str1,-1),'.',-3),substring_index(substring_index(substring_index(REPLACE(url,str2,str1), '/',3),str1,-1),'.',-2));
END;
//
mysql> select domain("http : //maps.google.com/maps?hl=en&q=what%20is%20domain%20name&btnG=Google+Search&ie=UTF-8&oe=UTF-8&um=1&sa=N&tab=il") DOMAIN;
+------------+
| DOMAIN |
+------------+
| google.com |
+------------+
1 row in set (0.00 sec)
similarly we can get the sub-domain too.
delimiter //
drop function if exists sub_domain;
CREATE FUNCTION sub_domain (url text(1000)) RETURNS CHAR(50)
BEGIN
DECLARE str1 varchar(10);
DECLARE str2 varchar(10);
SET str1=http : //;
SET str2=https : //;
RETURN if(substring_index(substring_index(substring_index(REPLACE(url,str2,str1), '/',3),str1,-1),'.',-1) != 'com',substring_index(substring_index(substring_index(REPLACE(url,str2,str1), '/',3),str1,-1),'.',-3),substring_index(substring_index(substring_index(REPLACE(url,str2,str1), '/',3),str1,-1),'.',-3));
END;
//
mysql> select sub_domain("http : //maps.google.com/maps?hl=en&q=what%20is%20domain%20name&btnG=Google+Search&ie=UTF-8&oe=UTF-8&um=1&sa=N&tab=il") sub_domain;
+-----------------+
| sub_domain |
+-----------------+
| maps.google.com |
+-----------------+
1 row in set (0.00 sec)
  Posted by Balaji Devarajan on March 24, 2007
I was looking for function, to give me the MOST COMMON VALUE IN A STRING. Used Java or php to do this, using substrCount and SplitString (thanks to Chris Stubben). I got the below function, which will give me the mcv value.

DELIMITER //
DROP FUNCTION IF EXISTS get_mcv;
CREATE FUNCTION get_mcv (list text(10000)) RETURNS text(1000)
BEGIN
DECLARE cnt int(10);
DECLARE iter_cnt int(10);
DECLARE item text(100);
DECLARE f_item text(100);
DECLARE prv_cnt int(10) default 0;
DECLARE nxt_cnt int(10) default 0;

IF list=' ' THEN
RETURN list;
END IF;

select substrCount(list,',')+1 into cnt;
SET iter_cnt = 1;

while cnt >= iter_cnt
do
select charsplit(list,',',iter_cnt) into item;

select substrCount(concat(',',list,','),concat(',',item,',')) into nxt_cnt;
IF nxt_cnt > prv_cnt THEN
SET prv_cnt = nxt_cnt;
SET f_item = item;
END IF;

set iter_cnt=iter_cnt+1;
end while;
RETURN f_item;

END
//

mysql> select get_mcv("dsfds,dsfds,fdfds,dfdsf,sd,df,df,df,df");
+---------------------------------------------------+
| get_mcv("dsfds,dsfds,fdfds,dfdsf,sd,df,df,df,df") |
+---------------------------------------------------+
| df |
+---------------------------------------------------+
1 row in set (0.02 sec)
  Posted by S D on March 28, 2007
A field may contain delimited values that may be used with 'IN' operator in a where clause. However each of the values need to be nested within single quote(').
This function uses stringSplit and substrCount - thanks to Chris Stubben.
CREATE FUNCTION cs2in(x varchar(255), delim varchar(12)) returns varchar(255) deterministic
BEGIN
DECLARE retstr varchar(255);
DECLARE Valcount INT(10);
DECLARE v1 INT(10);
SET retstr = '';
SET Valcount = substrCount(x,delim)+1;
SET v1=0;
WHILE (v1 < Valcount) DO
SET retstr = concat_ws(',',retstr,quote(stringSplit(x,delim,v1+1)));
SET v1 = v1 + 1;
END WHILE;
SET retstr = CONCAT('(',TRIM(LEADING ',' FROM TRIM(retstr)),')');
RETURN retstr;
END

E.g.
mysql> Select cs2in('1,2,3,4,5',',') as IN_format;
+---------------------+
| IN_format |
+---------------------+
|('1','2','3','4','5')|
+---------------------+

This format is compatible for use in the 'IN' clause.
  Posted by LEO DIVINAGRACIA on June 14, 2007
for a DIFFERENCE like function when comparing two strings together, try this:

------------------------------

DELIMITER $$

DROP FUNCTION IF EXISTS `db2`.`diff3`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `diff3`(n1 varchar(50), n2 varchar(50)) RETURNS int(11)
DETERMINISTIC
BEGIN
declare s1 char(1);
declare s2 char(1);
declare s3 int;
declare s4 int;
declare l1 int;
declare diff int;
set l1 = 1;
set diff = 0;
repeat
set s1 = substring(soundex(n1),l1,1);
set s2 = substring(soundex(n2),l1,1);
if s1 = s2 then set diff = diff + 1;
end if;
set l1 = l1 + 1;

until l1 > 4
end repeat;
return diff;
END$$

DELIMITER ;

----------------------

other DBMS have this function and i kinda needed one. so looked and mysql's online docs shows a DIFFERENCE function but that was for GIS apps and isnt current implemented.

just change the "user@hostname" and the "db.function_name" to reflect your info.

returns an INT value from 0 to 4, where 0 means the SOUNDEX of each string doesnt have any same value. 4 means each 4 alphanumeric digit is the same:

select soundex("hello"), soundex("jello")

returns

H400 and J400

so DIFF3("hello", "jello")

returns a 3

while DIFF3("hello","great")

returns a 1

as a stored function, you can do something like:

select firstname from mytable where diff3("joe bob", firstname) > 3

  Posted by Brett Millett on June 29, 2007
Just some syntax to pass along for those who may wanna reformat credit cards (if you are brave enough to store them as plain text in the first place) before sending them to an application for displaying. This lets you pad out all the numbers except the last four (all you developers have done this millions of times I'm sure.)

SELECT LPAD(SUBSTRING(`cardnumbercolumn`, -4, 4),LENGTH(`cardnumbercolumn`),'*') FROM table
  Posted by Nigel Forward on July 6, 2007
To format a number with leading zeros you can use LPAD:

eg: LPAD(13, 4, '0') returns '0013'

Any numbers that generate more than the number of digits (4 in this case) would be truncated from the left:

eg: LPAD(41278, 4, '0') returns '1278'
  Posted by ben j on September 4, 2007
Simple Split
SELECT SUBSTRING_INDEX( SUBSTRING_INDEX( 'a|b|c|d|e|f|g|h', '|', index), '|', -1 );

  Posted by Andrej Abehtikov on September 19, 2007
A simple way to convert IP address from string '0A0B0C0D' into 10.11.12.13 :
CONCAT(
ASCII(UNHEX(SUBSTRING(yourIP,1,2))), '.',
ASCII(UNHEX(SUBSTRING(yourIP,3,2))), '.',
ASCII(UNHEX(SUBSTRING(yourIP,5,2))), '.',
ASCII(UNHEX(SUBSTRING(yourIP,7,2)))
)
  Posted by Steven Benjamin on November 12, 2007
I sometimes need to find the last occurrence of a string. Using a previous post I did this by implementing the following procedure

delimiter ||
DROP FUNCTION IF EXISTS locatelast||
CREATE FUNCTION locatelast(s VARCHAR(1000), ss VARCHAR(1000)) RETURNS TINYINT(3) UNSIGNED LANGUAGE SQL NOT DETERMINISTIC READS SQL DATA
BEGIN
DECLARE last TINYINT(3) UNSIGNED;
DECLARE offset TINYINT(3) UNSIGNED;
DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET s = NULL;

SET last = 0;
SET offset = 1;

REPEAT
IF NOT ISNULL(s) AND offset > 0 THEN
SET offset = LOCATE(ss, s, offset);
IF offset > 0 THEN
SET last = offset;
SET offset = offset + 1;
END IF;
END IF;
UNTIL ISNULL(s) OR offset = 0 END REPEAT;

RETURN last;
END;

  Posted by Denis Roy on November 15, 2007
In response to Steven Benjamin on November 12 2007 7:53pm

Instead of looping through the string to look for the last occurrence, simply reverse() the string and look for the first occurrence, then substract the found position from the string length:

select @loc:=length(realname) - locate(" ", reverse(realname)) from table

For instance, looking for the last occurrence of a space?

select @string:="A horse with no name" as String, @loc:=length(@string) - locate(" ", reverse(@string))+1 AS lastoccurrence, left(@string, @loc), substr(@string,@loc+1);
+----------------------+----------------+---------------------+------------------------+
| String | lastoccurrence | left(@string, @loc) | substr(@string,@loc+1) |
+----------------------+----------------+---------------------+------------------------+
| A horse with no name | 16 | A horse with no | name |
+----------------------+----------------+---------------------+------------------------+

  Posted by Matias Alejo Garcia on November 28, 2007
It is important to check the value of group_concat_max_len
where using GROUP_CONCAT.

The default is 8192 (bytes), and if the result is bigger, it will be silently cropped, leading to unexpected results.
Some examples here: http://confronte.com.ar/groupconcat
  Posted by Axel Axel on December 14, 2007
If you want to compare an empty string to a numeric value or an integer field, you'll have to CAST the integer field or value to a string, due to the fact that for mysql, a zero (the integer one) equals to an empty string

Example :
SELECT 0 = '';
==> 1

SELECT '0' = '';
==> 0

SELECT CAST(0 AS CHAR) = '';
==> 0

This is common when you want to check user input : if a user inputs a "0" for a field, the check without cast will fail because mysql thinks this is an empty string.

  Posted by Grigory Dmitrenko on December 21, 2007
Just checked a lot of documentation and also didn't find any solution to split delimited string into an array (temporary table).
I know the example where it is needed to walk through the input string to find dilimiters but I think this way annoying.
You may use my solution from below which is also keeping the order of substring occurance:

(input string is stored in "input" variable)

CREATE TEMPORARY TABLE temp (id TINYINT NOT NULL auto_increment, val CHAR(20), PRIMARY KEY(id));
SET input=REPLACE(input, ",", "'),('");
SET @dyn_sql=CONCAT("INSERT INTO temp (val) VALUES ('",input,"');");
PREPARE s1 FROM @dyn_sql; EXECUTE s1;
SELECT * FROM temp;

Hope this would help someone :)
  Posted by robyn wyrick on February 29, 2008
In response to Denis Roy on November 15 2007 8:46pm

That is a great example. Here is how I used a very similar example to find a contact's last name from a contacts database by sub string on the last instance of the space:

SELECT @string:=Full_Name, SUBSTRING(@string, LENGTH(SUBSTRING(REVERSE(@string), LOCATE(" ", REVERSE(@string))-1))) AS Last_Name FROM contacts;

Something that would more elegant would be to have the LOCATE function include a direction option, like:

SELECT SUBSTRING(foo, LOCATE(" ", foo, RIGHT)) AS bar;

  Posted by Lu Yizhen on April 16, 2008
if you want to remove the tab(\t)
try this
update temp set locus=trim(BOTH ' ' from locus)
  Posted by horace borov on April 30, 2008
dudes & dudettes,

if you want to find the last occurrence of a particular string, use the tools mysql provides for you:

select reverse( substring( reverse( field ), locate( 'xyz', reverse( field ) )+1 ) )

---
this is way easier to implement and debug

  Posted by none dotcom on May 21, 2008
As i was in charge to support soundex compatible string comparison i had made following first mysql function.
Maybe it will help someone to find it's own and better solutions ;)

CREATE FUNCTION SOUNDEX_SEARCHTEXT( haystack LONGTEXT, needle VARCHAR(40) ) RETURNS INT
BEGIN
DECLARE part VARCHAR(40) DEFAULT SUBSTRING( haystack, 1, LENGTH(needle) );
DECLARE iterator INT DEFAULT 1;
WHILE iterator < LENGTH( haystack )-LENGTH(needle)+1 DO
SET iterator = iterator + 1;
SET part = SUBSTRING( haystack, iterator, LENGTH(needle) );
IF part SOUNDS LIKE needle THEN
RETURN 1;
END IF;
END WHILE;
RETURN 0;
END

Hope it will be usefull - with best regards
  Posted by Umesh Shastry on June 6, 2008
I was going thru the example given in earlier post about the INITCAP/UCFIRST fucnctionality. It was very useful for the strings without space.. below procedure would useful for those string having space in it.

DELIMITER $$
DROP FUNCTION IF EXISTS `initcap`$$
CREATE DEFINER=`root`@`%` FUNCTION `initcap`(x varchar(255)) RETURNS varchar(255) CHARSET utf8
begin
set @l_str='';
set @r_str='';


if x REGEXP ' ' then
SELECT SUBSTRING_INDEX(x, ' ',1) into @l_str;
SELECT SUBSTRING_INDEX(x, ' ',-1) into @r_str;
return concat(concat( upper(substring(@l_str,1,1)),lower(substring(@l_str,2))),' ',concat( upper(substring(@r_str,1,1)),lower(substring(@r_str,2))));

else

return concat( upper(substring(x,1,1)),lower(substring(x,2)));

end if;

end$$
DELIMITER ;







  Posted by YiXia SUN on August 26, 2008
In response to robyn wyrick on February 29 2008 7:01pm and Denis Roy on November 15 2007 8:46pm

Thank you for the hint!

Follow your examples I generate the following statement:
RIGHT(foo, locate(' ', REVERSE(foo))-1) as foo
  Posted by Alex Vekselman on September 7, 2008
Hello,

There are several stored procedures (e.g., see post of Grigory Dmitrenko) to transform
string like 'a,b,c' into something to be used like
....WHERE x IN ('a','b','c').

Here is solution to transform delimited string
into real table. Thus, it can be used further in
JOIN or IN constructs.

Pre-condition -- existence of some table with row count
bigger than elements in string. I will use
3-row table created on-fly by UNION.

mysql> select substring_index(substring_index('a,b,c', ',',@r:=@r+1),',',-1) zxz
from (select @r:=0) x,
(select 'x' xx union select 'v' xx union select 'z' xx) z;
+------+
| zxz |
+------+
| a |
| b |
| c |
+------+
3 rows in set (0.00 sec)

Thanks ben j for double *substring_index* example posted above.
  Posted by Luke Burgess on October 31, 2008
Chop off last 3 characters from a string. Cannot find an official way of doing this! This method works:

SELECT SUBSTRING(foobar,1,LENGTH(foobar)-3) AS foobar

  Posted by Michael Lisicki on November 16, 2008
I find this handy to extract the domain name (including subdomain) from an URL:

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(url,'://',-1),'/',1)
FROM urls

It works for URLs with and without http(s). But doesn't work if you have local URLs without a leading slash like "folder/index.html". In that case it extracts "folder" instead of an empty string.
  Posted by Ilde Giron on November 28, 2008
I recently found that after filling a table with info from a csv file created with MS Excel, an unwanted character went into the end of a field, and it showed up as "^M". So, when I issued a
mysql> select description from catalog;

the list looked all garbled

I used next command to remove it (most, but not all of the rows in the table were contaminated):
mysql> update catalog set description = left(description,length(description) -1) where description like "%^M%";

Please note that to replicate that "^M" you must press <ctrl> and v --though no character will be displayed-- and then <ctrl> and m.
  Posted by Steve Klein on February 16, 2009
You can use REVERSE to parse the last token from a string. This can be useful for name processing, for instance (first name is everything except last token and last name is last token):

SELECT
REVERSE(SUBSTR(REVERSE(name),INSTR(REVERSE(name),' ')+1)) AS first,
REVERSE(SUBSTR(REVERSE(name),1,INSTR(REVERSE(name),' '))) AS last
FROM table
  Posted by Phil Barone on March 6, 2009
Thanks Ilde for sharing your <control><m> example and especially how to type the <control><m> into the console.

One minor change, since you are only replacing the one character at the end is, change the where clause to

where description like "%^M";
  Posted by Matt Cavanagh on May 15, 2009
Was looking around trying to find out how to use the initcap functionality that Oracle has but mysql does not and came across the two suggestions posted above. The second example, however, is still not 100% accurate, as if there are more than 2 words in the data, it will capitalize the first and last words, and completely delete anything in between! I wanted to write a full version of this method:

-- ***********************************

DELIMITER $$
DROP FUNCTION IF EXISTS `initcap` $$
CREATE FUNCTION `initcap`(x char(30)) RETURNS char(30) CHARSET utf8
BEGIN
SET @str='';
SET @l_str='';
WHILE x REGEXP ' ' DO
SELECT SUBSTRING_INDEX(x, ' ', 1) INTO @l_str;
SELECT SUBSTRING(x, LOCATE(' ', x)+1) INTO x;
SELECT CONCAT(@str, ' ', CONCAT(UPPER(SUBSTRING(@l_str,1,1)),LOWER(SUBSTRING(@l_str,2)))) INTO @str;
END WHILE;
RETURN LTRIM(CONCAT(@str, ' ', CONCAT(UPPER(SUBSTRING(x,1,1)),LOWER(SUBSTRING(x,2)))));
END $$
DELIMITER ;

-- ***********************************

One gotcha to note: this method strips out any leading and trailing spaces from the input, which really isn't that big of a deal, but something to keep in mind.
  Posted by Ed Anderson on May 28, 2009
The ^M character is the DOS EOL character - and you can avoid the entire problem by dumping the file from Excel to a CSV file - if you're running in UNIX/Linux you can use the "dos2unix" utility which will strip out the ^M's and leave you with a portable file. Just my two cents.
  Posted by Kim TongHyun on July 23, 2009
I modified the function strSplit(from Chris Stubben) for utf8.

DROP FUNCTION IF EXISTS strSplit;
CREATE FUNCTION strSplit(x varchar(21845), delim varchar(255), pos int) returns varchar(255)
return replace(
replace(
substring_index(x, delim, pos),
substring_index(x, delim, pos - 1),
''
),
delim,
''
);

mysql> select strSplit("あ|ええ|いいい|おおお", '|', 4) as 4th;
+-----------+
| 4th |
+-----------+
| おおお |
+-----------+
  Posted by Chris Porter on August 28, 2009
re: to get the element at position x in a string..

instead of using the command:

select replace(
substring_index(field, delim, pos),
substring_index(field, delim, pos - 1),
'')

from table;

you can shorten it to require less modifiying by doing:

select substring_index(
substring_index(field, 'xyz', pos)
, 'xyz', -1)
from table;

that will get the last element of the list of x that were found. which should be the one you want.

hope this helps!

  Posted by Arlyn Johns on November 19, 2009
Here is another example of how to transform a comma separated string into a list of values that can be used in a WHERE x IN ('a','b','c') clause:

SELECT * from foo
WHERE FIND_IN_SET(col, REPLACE('a, b, c', ' ', '')) != 0;

  Posted by Orhan Dogan on November 21, 2009

count of '@' char:

SELECT
stringfield,
LENGTH(stringfield)-LENGTH(REPLACE(stringfield,'@',''))
FROM tablename

  Posted by Ernesto Spiro Peimbert Andreakis on December 29, 2009
Here is a function I created to simulate PHP's ucwords, I know it can be improved so you're welcome to do so:

CREATE FUNCTION `ucwords`(`string` text) RETURNS text CHARSET latin1
BEGIN
DECLARE final_string text default '';
DECLARE char_index int unsigned default 1;
DECLARE upperchar int unsigned default 1;

IF LENGTH(string)>0 THEN
IF LOCATE(' ',string) > 0 OR LOCATE('.',string) OR LOCATE('(',string) > 0 OR LOCATE('¿',string) THEN
REPEAT
IF upperchar = 1 THEN
SET final_string = CONCAT(final_string,UPPER(SUBSTRING(string,char_index,1)));
SET upperchar = 0;
ELSE
SET final_string = CONCAT(final_string,SUBSTRING(string,char_index,1));
END IF;
IF (SUBSTRING(string,char_index,1) = ' ') OR (SUBSTRING(string,char_index,1) = '.') OR (SUBSTRING(string,char_index,1) = '(') OR (SUBSTRING(string,char_index,1) = '¿') THEN
SET upperchar = 1;
END IF;
SET char_index = char_index + 1;
UNTIL char_index > LENGTH(string)
END REPEAT;
ELSE
SET final_string = CONCAT(UPPER(SUBSTRING(string,1,1)),SUBSTRING(string,2));
END IF;
ELSE
SET final_string = string;
END IF;
RETURN final_string;
END
  Posted by Claude Warren on February 10, 2010
I needed a way to parse UTF-8 strings into words, not finding any mechanism that would allow me to specify a list of characters to split on I hit upon using regexp and string manipulation to parse the string. The following is a function to find regex defined positions in a string and a procedure to break words out of a string based on regex.


delimiter $$

--
-- This function will return the first position in p_str where the regexp is true
--
drop function if exists regexPos $$
create function regexPos( p_str TEXT, p_regex varchar(250) ) returns int
BEGIN
declare v_pos int;
declare v_len int;
set v_pos=1;
set v_len=1+char_length( p_str );
while (( substr( p_str, 1, v_pos) REGEXP p_regex)=0 and (v_pos<v_len))
do
set v_pos = v_pos + 1;
end while;
return v_pos-1;
end $$

--
-- This procedure parses p_str into words based on the regular expression p_regex.
-- The simplest usage is call ParseWords( "some string", "[[:space:]]" );
-- this will break the string on spaces.
CREATE procedure ParseWords (IN p_str TEXT, IN p_regex varchar(256))
begin
declare v_startPos int;
declare v_strLen int;
declare v_wordLen int;
set v_startPos=1;
set v_strLen=char_length( p_str )+1;

while ( v_startPos < v_strLen )
do
set v_wordLen = regexPos( substring( p_str, v_startPos ), p_regex );
while (v_wordLen = 0) and ( v_startPos < v_strLen)
do
-- if the wordLen is 0 (zero) then we have a space at the start
-- so remove it and try again.
set v_startPos = v_startPos+1;
set v_wordLen = regexPos( substring( p_str, v_startPos ), p_regex );
end while;
if (v_wordLen > 0)
then
-- we found a word.
-- do something useful here. This example simply prints out the words
-- a real application will probably insert them into a table.
select substring( p_str, v_startPos, v_wordLen );
set v_startPos = v_startPos + v_wordLen +1;
end if;
end while;
end $$

delimiter ;

  Posted by Karl Walker on April 9, 2010
I was in need of a way to find the start position of a regex match in a string. I tried using regexPos above, but it seemed to be returning the end position of the match (minus 1). So, I modified it and called it rendpos, and used it to find the start position.

DELIMITER $$

DROP FUNCTION IF EXISTS `rendpos` $$
CREATE DEFINER=`root`@`localhost` FUNCTION `rendpos`(p_regex varchar(250),p_str TEXT) RETURNS int(11)
BEGIN

declare v_endpos int;
declare v_startpos int;
declare v_len int;

set v_endpos=1;
set v_len=1+char_length( p_str );
while (( substr( p_str, 1, v_endpos) REGEXP p_regex)=0 and (v_endpos<v_len))
do
set v_endpos = v_endpos + 1;
end while;

return v_endpos;

END $$

DELIMITER ;

Here is a quick and dirty find of start position. It will find the minimal match instead of the maximal pattern match. Please feel free to modify this to find the maximal pattern match.

DELIMITER $$

DROP FUNCTION IF EXISTS `rlocate` $$
CREATE DEFINER=`root`@`localhost` FUNCTION `rlocate`(p_regex varchar(250),p_str TEXT, s_startpos int) RETURNS int(11)
BEGIN
declare v_endpos int;
declare v_startpos int;
declare v_len int;

set v_endpos=rendpos(p_regex, p_str, s_startpos);

set v_startpos = v_endpos;
while (( substr( p_str, v_startpos, v_endpos) REGEXP p_regex)=0 and (v_startpos > 0))
do
set v_startpos = v_startpos - 1;
end while;

return v_startpos;
END $$

DELIMITER ;

The extract uses the above two functions, so it will likewise extract the minimal pattern.

DELIMITER $$

DROP FUNCTION IF EXISTS `rextract` $$
CREATE DEFINER=`root`@`localhost` FUNCTION `rextract`(p_regex varchar(250),p_str TEXT, s_startpos int) RETURNS varchar(250) CHARSET latin1
begin

declare startpos int;
declare endpos int;

set startpos = rlocate(p_regex,p_str,s_startpos);
set endpos = rendpos(p_regex,p_str,s_startpos);

return mid(p_str,startpos,endpos-startpos+1);

end $$

DELIMITER ;
  Posted by Vector Thorn on June 7, 2010
I don't know if anyone else ever needed to convert to base32, in a non-standardized way; but if so, i found a great way to do it here, and they even provide mysql functions for it:

http://ionisis.com/?a=WCMS_Page_Display&id=27576001275882717

  Posted by Asle Benoni on July 9, 2010
To update a text field and change all city names to Titlecase (propercase), this short code works:

UPDATE mytable SET city = CONCAT(UCASE(MID(city,1,1)),MID(LCASE(city),2))

So city names PARIS or paris will be changed to Paris.
  Posted by Carsten Meier on July 26, 2010
FIELD() doesn't work with multiple columns, e.g. FIELD((col1, col2), (11,12), (22,23)) aborts with error #1241.

To work around this limitation, one can use nested IF() functions like this:

IF((col1, col2)=(11,12), 1, IF((col1, col2)=(22,23), 2, 0))
  Posted by Mike Fehse on September 25, 2010
To expand a word, from an abbreviation to the full spelling, such as 'Ing:' to 'Ingredient(s):', or just inserting something without overwriting everything else, you can use the following:

UPDATE table_name AS t SET t.field_name = INSERT(t.field_name, 4, 0, 'redient(s)') WHERE LEFT(t.field_name, 4) = 'Ing:';

This inserts 'edient(s)' between the 'g' and ':' in 'Ing:', giving us 'Ingredient(s):' It also tests t.field_name to see if it is to be updated. This is based on knowing that the first three charters in t.field_name will be 'Ing:' or not, and if it is then we spell it out. You can even expand the spelling in the t.field_name, not just the start or end of it, as this might suggest. Use INSTR(t.field_name, 'str_to_expand'), so it would end up looking like:

UPDATE table_name AS t SET t.field_name = INSERT(t.field_name, INSTR(t.field_name, 'Ing:'), 0, 'redient(s)') WHERE LEFT(t.field_name, 4) = 'Ing:';

If you know that you have the abbreviation in more than just one place within a field (aka column) then just run the command again. In both cases the number zero '0' is the key, it tells the INSERT command not to overwrite any of the following charters, just insert the requested sub-string.
  Posted by Benjamin Bouraada on October 27, 2010
Stringcutting:

PROCEDURE Insert(IN STR_IN VARCHAR(255), IN ID_IN INT)
BEGIN
declare lang int default LENGTH(STR_IN);
declare sep char default ';';
declare tmpMerge char(255);
declare tmpChar char;
declare loop_done integer default 1;
stringcutter: loop
set tmpChar = substring(STR_IN,loop_done,1);
if tmpChar <> sep then
if isnull(tmpMerge) then set tmpMerge = tmpChar;
else select concat(tmpMerge,tmpChar)into tmpMerge;end if;end if;
if tmpChar = sep then DO WHAT YOU WANT;set tmpMerge = NULL;end if;
set loop_done = loop_done + 1;
if loop_done = lang then leave stringcutter;end if;
end loop stringcutter;
END
  Posted by yerke kz on January 24, 2011
my mysql split function:

DROP PROCEDURE IF EXISTS `SPLIT_STRING`;

DELIMITER |
CREATE PROCEDURE `SPLIT_STRING` (IN `MY_STRING` TEXT, IN `MY_DELIMITER` TEXT)
LANGUAGE SQL
SQL SECURITY INVOKER
BEGIN
#-------------------------------------------------------------------------------
IF NOT ISNULL(MY_STRING) THEN
IF NOT ISNULL(MY_DELIMITER) THEN
#
SET @SS = TRIM(MY_STRING);
SET @DEL = TRIM(MY_DELIMITER);
#
IF LENGTH(@SS) > 0 THEN
IF LENGTH(@DEL) > 0 THEN
#
SET @DP = (SELECT LOCATE(@DEL, @SS, 1));
IF @DP > 0 THEN
#------------------------CREATE TEMP TABLE-----------------------
DROP TABLE IF EXISTS `TEMPORARY_TABLE_OF_SPLIT_STRINGS`;
#
CREATE TEMPORARY TABLE `TEMPORARY_TABLE_OF_SPLIT_STRINGS` (
`SUB_STRING` text CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL
)
ENGINE=INNODB
CHARACTER SET utf8
COLLATE utf8_general_ci ;
#----------------------------------------------------------------
SET @SS_2 = @SS;
#
REPEAT
#
SET @FIRST_ELEMENT = (SELECT SUBSTRING_INDEX(@SS_2, @DEL, 1));
SET @SS_2 = (SELECT TRIM(LEADING CONCAT(@FIRST_ELEMENT, @DEL) FROM @SS_2));
#
INSERT INTO `TEMPORARY_TABLE_OF_SPLIT_STRINGS` (`SUB_STRING`) VALUES (@FIRST_ELEMENT);
SET @DP = (SELECT LOCATE(@DEL, @SS, @DP + 1));
#
IF @DP = 0 THEN
SET @LAST_ELEMENT = (SELECT SUBSTRING_INDEX(@SS_2, @DEL, -1));
INSERT INTO `TEMPORARY_TABLE_OF_SPLIT_STRINGS` (`SUB_STRING`) VALUES (@LAST_ELEMENT);
END IF;
UNTIL @DP = 0
END REPEAT;
#
SELECT * FROM TEMPORARY_TABLE_OF_SPLIT_STRINGS;
#----------------------------------------------------------------
DROP TABLE IF EXISTS `TEMPORARY_TABLE_OF_SPLIT_STRINGS`;
#----------------------------------------------------------------
ELSE
SELECT NULL;
END IF;
ELSE
SELECT NULL;
END IF;
ELSE
SELECT NULL;
END IF;
ELSE
SELECT NULL;
END IF;
ELSE
SELECT NULL;
END IF;
END; |
DELIMITER ;
  Posted by Juan Andrés Calleja on February 14, 2011
Hi, I found one usefully example in mysql forums (http://lists.mysql.com/mysql/199134) for split a varchar to use in the 'IN' clause in query. I create new input parameter with table name for use in dynamic CREATE table statement.

Thus split function can be used more than once in the same stored procedure because table have any name.

This is the SP. Excuse me for my bad english :(

DELIMITER $$

CREATE PROCEDURE `SplitString`( IN input TEXT,
IN delimiter VARCHAR(10), IN Table_name VARCHAR(50)
)
SQL SECURITY INVOKER
BEGIN
DECLARE cur_position INT DEFAULT 1 ;
DECLARE remainder TEXT;
DECLARE cur_string VARCHAR(1000);
DECLARE delimiter_length TINYINT UNSIGNED;


set @sql_drop = concat('DROP TEMPORARY TABLE IF EXISTS ',' ',Table_name);
prepare st_drop from @sql_drop;
execute st_drop;

set @sql_create = concat('CREATE TEMPORARY TABLE ' ,Table_name ,' (value VARCHAR(1000) NOT NULL PRIMARY KEY) ENGINE=MEMORY;');
prepare st_create from @sql_create;
execute st_create;

SET remainder = input;
SET delimiter_length = CHAR_LENGTH(delimiter);

WHILE CHAR_LENGTH(remainder) > 0 AND cur_position > 0 DO
SET cur_position = INSTR(remainder, delimiter);

IF cur_position = 0 THEN
SET cur_string = remainder;
ELSE
SET cur_string = LEFT(remainder, cur_position - 1);
END IF;

IF TRIM(cur_string) != '' THEN
set @sql_insert = concat('INSERT INTO ' ,Table_name, ' VALUES (',cur_string,');');
prepare st_insert from @sql_insert;
execute st_insert;
END IF;

SET remainder = SUBSTRING(remainder, cur_position +
delimiter_length);
END WHILE;
END

  Posted by shiva Kumar on February 17, 2011
Hi mysqlis,

Here the difference between the string functions LOCATE and FIND_IN_SET is..

1.When using LOCATE for integers use carefully..

example:
If I need to return 1 if 2 is in the set '1,2,3,4,5'.

SELECT IF(LOCATE(2,'1,2,3,4,5,6,7,8,9')>0,1,0);
You know very well it return 1,because the set contains value 2 in given set.
SO it is no problem...

FOR this Example query it returns wrong as we expected...

SELECT IF(LOCATE(2,'11,12,3,4,5,6,7,8,9')>0,1,0);
even though 2 is not available in set,it gives 1.

here LOCATE function takes the set as the STRING not the comma(,) separated value..

In this situation Please use the FIND_IN_SET - which is great function for the comma(,) separated value set.

Now,

SELECT IF(FIND_IN_SET(2,'11,12,3,4,5,6,7,8,9')>0,1,0);

It returns 1 as we expected...

Note:
1.Use LOCATE function for alphabetic strings only..
2.And also use LOCATE for numeric numbers that set contains the numbers only 0,1,2,3,4,5,6,7,8,9

i.e.,

SELECT IF(LOCATE(input,'0,1,2,3,4,5,6,7,8,9')>0,1,0);

input must be any one within 0,1,2,3,4,5,6,7,8,9
Its work nicely.

  Posted by Vector Thorn on April 9, 2011
Hi guys. For those of you who are trying to do a string replace on a string that contains a wildcard, you can actually write your own UDF to solve that, as i did here:

http://thesocialexpo.com/?a=SUBS_Blog_Display&id=13023741560341786
  Posted by Lies DJILLALI on August 31, 2011
Thank you Giovanni for your strip_tags function,

Here is a patched version because Mysql crashed when I tryied to proceed a NULL value

delimiter ||

DROP FUNCTION IF EXISTS strip_tags||
CREATE FUNCTION strip_tags( x longtext) RETURNS longtext
LANGUAGE SQL NOT DETERMINISTIC READS SQL DATA
BEGIN
DECLARE sstart INT UNSIGNED;
DECLARE ends INT UNSIGNED;
IF x IS NOT NULL THEN
SET sstart = LOCATE('<', x, 1);
REPEAT
SET ends = LOCATE('>', x, sstart);
SET x = CONCAT(SUBSTRING( x, 1 ,sstart -1) ,SUBSTRING(x, ends +1 )) ;
SET sstart = LOCATE('<', x, 1);
UNTIL sstart < 1 END REPEAT;
END IF;
return x;
END;
||
delimiter ;

mysql> SELECT strip_tags('<a href="HelloWorld.html"><B>Hi, mate!</B></a>') as strip_tags;

+------------+
| strip_tags |
+------------+
| Hi, mate! |
+------------+
  Posted by Steven Gath on October 31, 2011
I was looking for an initcap or ucfirst function that would uppercase the first letter of each word in a string and couldn't find one so I modified one of the functions here so it worked for any number of words. Hope it can help someone else.

DELIMITER $$
DROP FUNCTION IF EXISTS `initcap`$$
CREATE FUNCTION `initcap`(x varchar(255)) RETURNS varchar(255) CHARSET utf8
DETERMINISTIC
begin
set @out_str='';
set @l_str='';
set @r_str='';

set @pos=LOCATE(' ',x);
SELECT x into @r_str;
while (@pos > 0) DO
SELECT SUBSTRING(@r_str,1,@pos-1) into @l_str;
SELECT SUBSTRING(@r_str,@pos+1) into @r_str;
SELECT concat(@out_str,upper(substring(@l_str,1,1)),lower(substring(@l_str,2)),' ') into @out_str;
set @pos=LOCATE(' ',@r_str);
END WHILE;
SELECT concat(@out_str,upper(substring(@r_str,1,1)),lower(substring(@r_str,2))) into @out_str;
return trim(@out_str);
end$$

DELIMITER ;
  Posted by Paul Caskey on November 10, 2011
For DATE and DATETIME operations, MySQL demands the year be first, then month, then day. In the USA, a common date format is month-day-year . This example converts a date from MM-DD-YYYY format to MySQL's preferred YYYY-MM-DD. It also works on M-D-YY input, or other shortcut forms. Change the '-' separate to '.' or whatever you need. This takes 6-13-2011 and returns a STRING of '2011-6-13':

SELECT CONCAT(SUBSTRING_INDEX(DateMDY, '-', -1), '-', SUBSTRING_INDEX(DateMDY, '-', 2))

Now you can CAST this to a DATE, and then it will ORDER BY or GROUP BY properly. E.g. this takes '11.1.2011' and returns a real DATE of 2011-11-01. As usual I'm sure there are other ways to do this. I was just happy to figure this out without resorting to PHP or Perl.

CAST(CONCAT(SUBSTRING_INDEX(DateMDY, '.', -1), '.', SUBSTRING_INDEX(DateMDY, '.', 2)) AS DATE)

  Posted by Manish Singh on November 17, 2011
If column of a table contains JSON string, then we can extract the value corresponding to a json key:

select substring_index(substring_index(json_params_column, 'jsonKey":"', -1), '"', 1) from MyTable;
  Posted by Jesse Perring on December 16, 2011
To split a field out into one row for each separator in the field (i.e. if you have a field with a variable number of comma separated values in each row, but you want a table with a row for every value in that list):

The table I started with was something like...
id, list_of_types
(champion_1), (mage, fighter, support)
(champion_2), (support, mage)
(champion_3), (tank, support)

and the table I needed was....
id, type
champion_1, mage
champion_1, fighter
champion_1, support
champion_2, support
champion_3, tank
champion_3, support

So I ran...

select tOut.*, replace(substring(substring_index(type, ',', ocur_rank), length(substring_index(type, ',', ocur_rank - 1)) + 1), ',', '')
from (select @num_type := if(@id_check = tY.id, @num_type + 1, 1) as ocur_rank, @id_check := tY.id as id_check, tY.*
from (select LENGTH(list) - length(replace(list, ',', '')) as num_ocur, id, list from item) tX
inner join (select LENGTH(list) - length(replace(list, ',', '')) as num_ocur, id, list from item) tY
inner join (select @num_type := 0, @id_check := 'some_id') tZ) tOut
where ocur_rank <= num_ocur + 1;

Where "id" is just some unique identifier for each field you're splitting up and "list" is the list of separated values. The thought behind the query is to just join a table to itself, rank the rows for each id, then only show rows where the rank is less than the number of occurrences of the separator in the list you're splitting up. The outter most select then shows the value in between the rank and rank + 1 occurrence of the separator in the list.

This may not work if some of the lists don't have any occurrence of the separator.

  Posted by Joseph Edmonds on January 19, 2012
Note concat can be used to compare two columns in the same query

so if you want to check if the contents of one column are in another column

http://www.edmondscommerce.co.uk/mysql/compare-two-columns-in-mysql/
  Posted by halászsándor halászsándor on February 13, 2012
I had the same problem that Edmonds described, and for that I used this expression:

LOCATE(col1, col2) > 0 -- if "col1" is found in "col2"
OR
LOCATE(col2, col1) > 0 -- if "col2" is found in "col1"
  Posted by Jez Gomez on April 18, 2012
I wanted to get the first portion of an email address, before the @ (ie, left of the @):

SELECT SUBSTRING_INDEX(email,'@',1) FROM <table> WHERE email REGEXP '@'
  Posted by Mariano Otero on June 22, 2012
MySQL does not include a function to split a delimited string. However, it’s very easy to create your own function. I've added an example here: http://www.indumental.com/in/software/mysql.html. If you follow the example on that page, you'll be able to do something like this:

SELECT SPLIT_STR('a|bb|ccc|dd', '|', 3) as third;

-Mo

  Posted by Alexandre Nunes on July 6, 2012
Suppose you have a text column with some delimiter separated data, and you want to get tokens from it, i.e. like strtok() would.

Ex, for the text "0,1,3,5,6", you wanna get the third element. This would do the trick:

select substring_index(substring_index(column,',',3),',',-1) as third;

P.S..: This seems a simplification of the previous example (which I managed to miss)
  Posted by die manto on February 7, 2013
Tip to compare two columns:

SELECT *
FROM
`table`
WHERE
`col1` LIKE CONCAT('%', `col2`, '%')
OR col2 LIKE CONCAT('%',`col1`,'%')

Posted by http://www.competenciaperfecta.com/

  Posted by Gunter Sammet on April 5, 2013
I was looking for a PHP equivalent for strpos and strrpos to get in combination with substring the string after the last occurrence of a character. Have a look at MYSQL SUBSTRING_INDEX. It may does what you want.
One of the first search results on another website suggested to use the locate function and if you need the last occurrence, use reverse string before using locate. Then use reverse again to get the correct sting. Just thought I'll post here with the important keywords, so it shows up in search results in case somebody else is looking for the same. HTH
  Posted by Biniam Kefale on May 31, 2013
Example of using CONCAT() and UPDATE

This code updates the column named 'phone_number' in the table called 'user' by concatenating '0' in front of the new phone_number.

The new phone_number is old phone_number minus the first 4 characters or beginning from the 5th character.

The update will only be applied to the records with id between 3 and 30 exclusive.

UPDATE user SET phone_number = CONCAT('0', SUBSTRING(phone_number, 5)) WHERE id > 3 AND id < 30;

See how the code is shorter than the explanation?

Biniam from Ethiopia.
  Posted by Adrian Humphreys on February 22, 2014
Here's a function to Propercase all the words in a string:

CREATE FUNCTION fn_propercase
(p_string Varchar(254)) RETURNS Varchar
BEGIN
SET @out="";
SET @x = 1;
SET @len = LENGTH(p_string);
/* Always make the 1st char uppercase. Set the flag on. */
SET @uc = 1;

REPEAT
SET @char= MID(p_string,@x,1);
IF @uc=1 THEN
SET @out= CONCAT(@out,UPPER(@char));
ELSE
SET @out= CONCAT(@out,LOWER(@char)) ;
END IF;

/* AFTER the char is written, test whether it is blank
if so, the NEXT char will be uppercase. */
IF @char=" " THEN
SET @uc= 1;
ELSE
SET @uc= 0;
END IF;

SET @x= @x + 1;
UNTIL @x > @len END REPEAT;

RETURN @out;

END
  Posted by Shivakumar Durg on August 7, 2014
The following formula can be used to extract the Nth item in a delimited list.

SET @str:='mba,bca,mca,Bed'; # Your Complete String
SET @length:=LENGTH(@str);
SET @limit:=@length-LENGTH(REPLACE(@str,',',''))+1;
SET @pos:=2; # Substring position value
SET @tmp:=REVERSE(SUBSTRING_INDEX(@str,',',@pos));
SELECT IF(@limit>=@pos,
IF(@pos=1,SUBSTRING_INDEX(@str,',',@pos),REVERSE(SUBSTRING(@tmp,1,LOCATE(',',@tmp)-1))),'Not Exist')AS "Required_String"
  Posted by EE Durham on August 10, 2014
Many thanks to Adrian Humphreys for his Propercase / Titlecase example: great idea :) Couldn't get it to work as-is, but here is a working version :)
Cheers!

DROP FUNCTION IF EXISTS str_titlecase;
CREATE FUNCTION str_titlecase (p_string varchar(254)) RETURNS varchar (254)
## by Adrian Humphreys, edited by Durham
## for given string, concatenate Capitalized first letter of
## each given word with Lower Case remainder of word
BEGIN
DECLARE output_string VARCHAR(254) DEFAULT '';
DECLARE temp_string VARCHAR(254);
DECLARE x INT DEFAULT 1; /*tracking variable*/
DECLARE uc INT DEFAULT 1; /*uppercase flag*/
DECLARE input_string_length INT DEFAULT LENGTH(p_string);

IF p_string IS NOT NULL THEN
REPEAT
SET temp_string := MID(p_string,x,1);
IF uc=1 THEN
SET output_string := CONCAT(output_string,UPPER(temp_string));
ELSE
SET output_string := CONCAT(output_string,LOWER(temp_string)) ;
END IF;

/* AFTER the char is written, test whether it is blank
if so, the NEXT char will be uppercase. */
IF temp_string=' ' THEN
SET uc := 1;
ELSE
SET uc := 0;
END IF;

SET x := x + 1;
UNTIL x > input_string_length END REPEAT;
END IF;

RETURN output_string;

END

#########################
## Usage (all lower case input):
select str_titlecase('i am a cat') as title from dual;

## Results:
title
------
I Am A Cat

## Usage (blank string case):
select str_titlecase('') as title from dual;

## Results:
title
------

## Usage (all upper case input):
select str_titlecase('I AM A DOLPHIN') as title from dual;

## Results:
title
------
I Am A Dolphin

## Usage (mixed-case input):
select str_titlecase('I am THE PRODUCT of your IMAGinatioN') as title from dual;

## Results:
title
------
I Am The Product Of Your Imagination

  Posted by Luis Rocha on March 27, 2015
Found this http://stackoverflow.com/a/18218191 but it would not work correctly. So I wrote my own function based on that. You might want to filter the results a bit before calling this function (i.e. "SELECT * FROM abc WHERE haystack LIKE '%needle%' AND hasString(haystack, 'needle')..."). It runs rather slow otherwise.

CREATE FUNCTION `hasString`(haystack TINYTEXT, needle TINYTEXT) RETURNS TINYINT(1)
BEGIN
DECLARE needleFound TINYINT(1);
DECLARE inipos INTEGER;
DECLARE endpos INTEGER;
DECLARE maxlen INTEGER;
DECLARE item VARCHAR(100);
DECLARE delim VARCHAR(1);

SET delim = ',';
SET inipos = 1;
SET endpos = 0;
SET needleFound = 0;
SET maxlen = LENGTH(haystack);

REPEAT
SET endpos = LOCATE(delim, haystack, inipos);
SET item = SUBSTR(haystack, inipos, endpos - inipos);

IF inipos = 1 AND endpos = 0 THEN
IF haystack = needle THEN
SET needleFound = 1;
END IF;
SET endpos = maxlen + 100;
ELSE
IF inipos > 1 AND endpos = 0 THEN
SET endpos = maxlen + 50;
ELSE
IF item <> '' AND item IS NOT NULL THEN
IF item=needle THEN
SET needleFound = 1;
END IF;
ELSE
SET inipos = maxlen + 10;
END IF;
END IF;
END IF;
SET inipos = endpos + 1;
UNTIL inipos >= maxlen END REPEAT;

RETURN needleFound;
END
  Posted by Jens Walte on April 29, 2015
fastest split() function

/**
* #1: this way is 10-20% faster than #3 and supports not included indexes otherwise than #2
*
* @example: split('a|bbb|cc', '|', 0) -> 'a'
* @example: split('a|bbb|cc', '|', 1) -> 'bbb'
* @example: split('a|bbb|cc', '|', 2) -> 'cc'
* @example: split('a|bbb|cc', '|', 3) -> ''
*/
substring_index(substring_index(concat(content, delimiter), delimiter, index+1), delimiter, -1);

/**
* #2: faster than #3, but not included index will return last entry
*
* @see: Posted by Mariano Otero on June 22 2012 3:43pm
* @example: split('a|bbb|cc', '|', 0) -> 'a'
* @example: split('a|bbb|cc', '|', 1) -> 'bbb'
* @example: split('a|bbb|cc', '|', 2) -> 'cc'
* @example: split('a|bbb|cc', '|', 3) -> 'cc' (unexpected)
*/
substring_index(substring_index(content, delimiter, index+1), delimiter, -1);

/**
* #3: first introduced split example, supports not included indexes
*
* @see: Posted by Bob Collins on March 17 2006 8:56pm
* @example: split('a|bbb|cc', '|', 0) -> 'a'
* @example: split('a|bbb|cc', '|', 1) -> 'bbb'
* @example: split('a|bbb|cc', '|', 2) -> 'cc'
* @example: split('a|bbb|cc', '|', 3) -> ''
*/
replace(substring(substring_index(content, delimiter, index+1), length(substring_index(content, delimiter, index)) + 1), delimiter, '');

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