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Excerpts from this Manual

MySQL 5.7 Reference Manual  /  MySQL 5.7 Frequently Asked Questions  /  MySQL 5.7 FAQ: MySQL Chinese, Japanese, and Korean Character Sets

A.11 MySQL 5.7 FAQ: MySQL Chinese, Japanese, and Korean Character Sets

This set of Frequently Asked Questions derives from the experience of MySQL's Support and Development groups in handling many inquiries about CJK (Chinese-Japanese-Korean) issues.

A.11.1. What CJK character sets are available in MySQL?
A.11.2. I have inserted CJK characters into my table. Why does SELECT display them as “?” characters?
A.11.3. What problems should I be aware of when working with the Big5 Chinese character set?
A.11.4. Why do Japanese character set conversions fail?
A.11.5. What should I do if I want to convert SJIS 81CA to cp932?
A.11.6. How does MySQL represent the Yen (¥) sign?
A.11.7. Of what issues should I be aware when working with Korean character sets in MySQL?
A.11.8. Why do I get Incorrect string value error messages?
A.11.9. Why does my GUI front end or browser display CJK characters incorrectly in my application using Access, PHP, or another API?
A.11.10. I've upgraded to MySQL 5.7. How can I revert to behavior like that in MySQL 4.0 with regard to character sets?
A.11.11. Why do some LIKE and FULLTEXT searches with CJK characters fail?
A.11.12. How do I know whether character X is available in all character sets?
A.11.13. Why do CJK strings sort incorrectly in Unicode? (I)
A.11.14. Why do CJK strings sort incorrectly in Unicode? (II)
A.11.15. Why are my supplementary characters rejected by MySQL?
A.11.16. Should “CJK” be “CJKV”?
A.11.17. Does MySQL permit CJK characters to be used in database and table names?
A.11.18. Where can I find translations of the MySQL Manual into Chinese, Japanese, and Korean?
A.11.19. Where can I get help with CJK and related issues in MySQL?

A.11.1.

What CJK character sets are available in MySQL?

The list of CJK character sets may vary depending on your MySQL version. For example, the gb18030 character set is not supported prior to MySQL 5.7.4. However, since the name of the applicable language appears in the DESCRIPTION column for every entry in the INFORMATION_SCHEMA.CHARACTER_SETS table, you can obtain a current list of all the non-Unicode CJK character sets using this query:

mysql> SELECT CHARACTER_SET_NAME, DESCRIPTION
       FROM INFORMATION_SCHEMA.CHARACTER_SETS
       WHERE DESCRIPTION LIKE '%Chin%'
       OR DESCRIPTION LIKE '%Japanese%'
       OR DESCRIPTION LIKE '%Korean%'
       ORDER BY CHARACTER_SET_NAME;
+--------------------+---------------------------------+
| CHARACTER_SET_NAME | DESCRIPTION                     |
+--------------------+---------------------------------+
| big5               | Big5 Traditional Chinese        |
| cp932              | SJIS for Windows Japanese       |
| eucjpms            | UJIS for Windows Japanese       |
| euckr              | EUC-KR Korean                   |
| gb18030            | China National Standard GB18030 |
| gb2312             | GB2312 Simplified Chinese       |
| gbk                | GBK Simplified Chinese          |
| sjis               | Shift-JIS Japanese              |
| ujis               | EUC-JP Japanese                 |
+--------------------+---------------------------------+

(For more information, see Section 22.1, “The INFORMATION_SCHEMA CHARACTER_SETS Table”.)

MySQL supports three variants of the GB (Guojia Biaozhun, or National Standard, or Simplified Chinese) character sets which are official in the People's Republic of China: gb2312, gbk, and (as of MySQL 5.7.4) gb18030.

Sometimes people try to insert gbk characters into gb2312, and it works most of the time because gbk is a superset of gb2312. But eventually they try to insert a rarer Chinese character and it does not work. (For an example, see Bug #16072).

Here, we try to clarify exactly what characters are legitimate in gb2312 or gbk, with reference to the official documents. Please check these references before reporting gb2312 or gbk bugs:

It is also possible to store CJK characters in Unicode character sets, although the available collations may not sort characters quite as you expect:

  • The utf8 and ucs2 character sets support the characters from Unicode Basic Multilingual Plane (BMP). These characters have code point values between U+0000 and U+FFFF.

  • The utf8mb4, utf16, utf16le, and utf32 character sets support BMP characters, as well as supplementary characters that lie outside the BMP. Supplementary characters have code point values between U+10000 and U+10FFFF.

The collation used for a Unicode character set determines the ability to sort (that is, distinguish) characters in the set:

  • Collations based on Unicode Collation Algorithm (UCA) 4.0.0 distinguish only BMP characters.

  • Collations based on UCA 5.2.0 or 9.0.0 distinguish BMP and supplementary characters.

  • Non-UCA collations may not distinguish all Unicode characters. For example, the utf8mb4 default collation is utf8mb4_general_ci, which distinguishes only BMP characters.

Moreover, distinguishing characters is not the same as ordering them per the conventions of a given CJK language. Currently, MySQL has only one CJK-specific UCA collation, gb18030_unicode_520_ci (which requires use of the non-Unicode gb18030 character set).

For information about Unicode collations and their differentiating properties, including collation properties for supplementary characters, see Section 11.1.10.1, “Unicode Character Sets”.

A.11.2.

I have inserted CJK characters into my table. Why does SELECT display them as ? characters?

This problem is usually due to a setting in MySQL that does not match the settings for the application program or the operating system. Here are some common steps for correcting these types of issues:

  • Be certain of what MySQL version you are using.

    Use the statement SELECT VERSION(); to determine this.

  • Make sure that the database is actually using the desired character set.

    People often think that the client character set is always the same as either the server character set or the character set used for display purposes. However, both of these are false assumptions. You can make sure by checking the result of SHOW CREATE TABLE tablename or, better yet, by using this statement:

    SELECT character_set_name, collation_name
        FROM information_schema.columns
        WHERE table_schema = your_database_name
            AND table_name = your_table_name
            AND column_name = your_column_name;
    
  • Determine the hexadecimal value of the character or characters that are not being displayed correctly.

    You can obtain this information for a column column_name in the table table_name using the following query:

    SELECT HEX(column_name)
    FROM table_name;
    

    3F is the encoding for the ? character; this means that ? is the character actually stored in the column. This most often happens because of a problem converting a particular character from your client character set to the target character set.

  • Make sure that a round trip is possible. When you select literal (or _introducer hexadecimal-value), do you obtain literal as a result?

    For example, the Japanese Katakana character Pe (ペ') exists in all CJK character sets, and has the code point value (hexadecimal coding) 0x30da. To test a round trip for this character, use this query:

    SELECT 'ペ' AS `ペ`;         /* or SELECT _ucs2 0x30da; */
    

    If the result is not also , the round trip failed.

    For bug reports regarding such failures, we might ask you to follow up with SELECT HEX('ペ');. Then we can determine whether the client encoding is correct.

  • Make sure that the problem is not with the browser or other application, rather than with MySQL.

    Use the mysql client program to accomplish this task. If mysql displays characters correctly but your application does not, your problem is probably due to system settings.

    To determine your settings, use the SHOW VARIABLES statement, whose output should resemble what is shown here:

    mysql> SHOW VARIABLES LIKE 'char%';
    +--------------------------+----------------------------------------+
    | Variable_name            | Value                                  |
    +--------------------------+----------------------------------------+
    | character_set_client     | utf8                                   |
    | character_set_connection | utf8                                   |
    | character_set_database   | latin1                                 |
    | character_set_filesystem | binary                                 |
    | character_set_results    | utf8                                   |
    | character_set_server     | latin1                                 |
    | character_set_system     | utf8                                   |
    | character_sets_dir       | /usr/local/mysql/share/mysql/charsets/ |
    +--------------------------+----------------------------------------+
    

    These are typical character-set settings for an international-oriented client (notice the use of utf8 Unicode) connected to a server in the West (latin1 is a West Europe character set).

    Although Unicode (usually the utf8 variant on Unix, and the ucs2 variant on Windows) is preferable to Latin, it is often not what your operating system utilities support best. Many Windows users find that a Microsoft character set, such as cp932 for Japanese Windows, is suitable.

    If you cannot control the server settings, and you have no idea what setting your underlying computer uses, try changing to a common character set for the country that you're in (euckr = Korea; gb18030, gb2312 or gbk = People's Republic of China; big5 = Taiwan; sjis, ujis, cp932, or eucjpms = Japan; ucs2 or utf8 = anywhere). Usually it is necessary to change only the client and connection and results settings. The SET NAMES. statement changes all three at once. For example:

    SET NAMES 'big5';
    

    Once the setting is correct, you can make it permanent by editing my.cnf or my.ini. For example you might add lines looking like these:

    [mysqld]
    character-set-server=big5
    [client]
    default-character-set=big5
    

    It is also possible that there are issues with the API configuration setting being used in your application; see Why does my GUI front end or browser not display CJK characters correctly...? for more information.

A.11.3.

What problems should I be aware of when working with the Big5 Chinese character set?

MySQL supports the Big5 character set which is common in Hong Kong and Taiwan (Republic of China). The MySQL big5 character set is in reality Microsoft code page 950, which is very similar to the original big5 character set.

A feature request for adding HKSCS extensions has been filed. People who need this extension may find the suggested patch for Bug #13577 to be of interest.

A.11.4.

Why do Japanese character set conversions fail?

MySQL supports the sjis, ujis, cp932, and eucjpms character sets, as well as Unicode. A common need is to convert between character sets. For example, there might be a Unix server (typically with sjis or ujis) and a Windows client (typically with cp932).

In the following conversion table, the ucs2 column represents the source, and the sjis, cp932, ujis, and eucjpms columns represent the destinations; that is, the last 4 columns provide the hexadecimal result when we use CONVERT(ucs2) or we assign a ucs2 column containing the value to an sjis, cp932, ujis, or eucjpms column.

Character Nameucs2sjiscp932ujiseucjpms
BROKEN BAR00A63F3F8FA2C33F
FULLWIDTH BROKEN BARFFE43FFA553F8FA2
YEN SIGN00A53F3F203F
FULLWIDTH YEN SIGNFFE5818F818FA1EF3F
TILDE007E7E7E7E7E
OVERLINE203E3F3F203F
HORIZONTAL BAR2015815C815CA1BDA1BD
EM DASH20143F3F3F3F
REVERSE SOLIDUS005C815F5C5C5C
FULLWIDTH ""FF3C3F815F3FA1C0
WAVE DASH301C81603FA1C13F
FULLWIDTH TILDEFF5E3F81603FA1C1
DOUBLE VERTICAL LINE201681613FA1C23F
PARALLEL TO22253F81613FA1C2
MINUS SIGN2212817C3FA1DD3F
FULLWIDTH HYPHEN-MINUSFF0D3F817C3FA1DD
CENT SIGN00A281913FA1F13F
FULLWIDTH CENT SIGNFFE03F81913FA1F1
POUND SIGN00A381923FA1F23F
FULLWIDTH POUND SIGNFFE13F81923FA1F2
NOT SIGN00AC81CA3FA2CC3F
FULLWIDTH NOT SIGNFFE23F81CA3FA2CC

Now consider the following portion of the table.

 ucs2sjiscp932
NOT SIGN00AC81CA3F
FULLWIDTH NOT SIGNFFE23F81CA

This means that MySQL converts the NOT SIGN (Unicode U+00AC) to sjis code point 0x81CA and to cp932 code point 3F. (3F is the question mark (?. This is what is always used when the conversion cannot be performed.)

A.11.5.

What should I do if I want to convert SJIS 81CA to cp932?

Our answer is: ?. There are disadvantages to this, and many people would prefer a loose conversion, so that 81CA (NOT SIGN) in sjis becomes 81CA (FULLWIDTH NOT SIGN) in cp932.

A.11.6.

How does MySQL represent the Yen (¥) sign?

A problem arises because some versions of Japanese character sets (both sjis and euc) treat 5C as a reverse solidus (\, also known as a backslash), whereas others treat it as a yen sign (¥).

MySQL follows only one version of the JIS (Japanese Industrial Standards) standard description. In MySQL, 5C is always the reverse solidus (\).

A.11.7.

Of what issues should I be aware when working with Korean character sets in MySQL?

In theory, while there have been several versions of the euckr (Extended Unix Code Korea) character set, only one problem has been noted. We use the ASCII variant of EUC-KR, in which the code point 0x5c is REVERSE SOLIDUS, that is \, instead of the KS-Roman variant of EUC-KR, in which the code point 0x5c is WON SIGN (). This means that you cannot convert Unicode U+20A9 to euckr:

mysql> SELECT
           CONVERT('₩' USING euckr) AS euckr,
           HEX(CONVERT('₩' USING euckr)) AS hexeuckr;
+-------+----------+
| euckr | hexeuckr |
+-------+----------+
| ?     | 3F       |
+-------+----------+

A.11.8.

Why do I get Incorrect string value error messages?

To see the problem, create a table with one Unicode (ucs2) column and one Chinese (gb2312) column.

mysql> CREATE TABLE ch
       (ucs2 CHAR(3) CHARACTER SET ucs2,
       gb2312 CHAR(3) CHARACTER SET gb2312);

In nonstrict SQL mode, try to place the rare character in both columns.

mysql> SET sql_mode = '';
mysql> INSERT INTO ch VALUES ('A汌B','A汌B');
Query OK, 1 row affected, 1 warning (0.00 sec)

The INSERT produces a warning. Use the following statement to see what it is:

mysql> SHOW WARNINGS\G
*************************** 1. row ***************************
  Level: Warning
   Code: 1366
Message: Incorrect string value: '\xE6\xB1\x8CB' for column 'gb2312' at row 1

So it is a warning about the gb2312 column only.

mysql> SELECT ucs2,HEX(ucs2),gb2312,HEX(gb2312) FROM ch;
+-------+--------------+--------+-------------+
| ucs2  | HEX(ucs2)    | gb2312 | HEX(gb2312) |
+-------+--------------+--------+-------------+
| A汌B | 00416C4C0042 | A?B    | 413F42      |
+-------+--------------+--------+-------------+

Several things need explanation here:

  1. The character is not in the gb2312 character set, as described earlier.

  2. If you are using an old version of MySQL, you may see a different message.

  3. A warning occurs rather than an error because MySQL is not set to use strict SQL mode. In nonstrict mode, MySQL tries to do what it can, to get the best fit, rather than give up. With strict SQL mode, the Incorrect string value message occurs as an error rather than a warning, and the INSERT fails.

A.11.9.

Why does my GUI front end or browser display CJK characters incorrectly in my application using Access, PHP, or another API?

Obtain a direct connection to the server using the mysql client, and try the same query there. If mysql responds correctly, the trouble may be that your application interface requires initialization. Use mysql to tell you what character set or sets it uses with the statement SHOW VARIABLES LIKE 'char%';. If you are using Access, you are most likely connecting with Connector/ODBC. In this case, you should check Configuring Connector/ODBC. If, for example, you use big5, you would enter SET NAMES 'big5'. (In this case, no ; character is required.) If you are using ASP, you might need to add SET NAMES in the code. Here is an example that has worked in the past:

<%
Session.CodePage=0
Dim strConnection
Dim Conn
strConnection="driver={MySQL ODBC 3.51 Driver};server=server;uid=username;" \
               & "pwd=password;database=database;stmt=SET NAMES 'big5';"
Set Conn = Server.CreateObject("ADODB.Connection")
Conn.Open strConnection
%>

In much the same way, if you are using any character set other than latin1 with Connector/Net, you must specify the character set in the connection string. See Connecting to MySQL Using Connector/Net, for more information.

If you are using PHP, try this:

<?php
  $link = new mysqli($host, $usr, $pwd, $db);

  if( mysqli_connect_errno() )
  {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
  }

  $link->query("SET NAMES 'utf8'");
?>

In this case, we used SET NAMES to change character_set_client, character_set_connection, and character_set_results.

Another issue often encountered in PHP applications has to do with assumptions made by the browser. Sometimes adding or changing a <meta> tag suffices to correct the problem: for example, to insure that the user agent interprets page content as UTF-8, include <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> in the <head> section of the HTML page.

If you are using Connector/J, see Using Character Sets and Unicode.

A.11.10.

I've upgraded to MySQL 5.7. How can I revert to behavior like that in MySQL 4.0 with regard to character sets?

In MySQL Version 4.0, there was a single global character set for both server and client, and the decision as to which character to use was made by the server administrator. This changed starting with MySQL Version 4.1. What happens now is a handshake, as described in Section 11.1.4, “Connection Character Sets and Collations”:

When a client connects, it sends to the server the name of the character set that it wants to use. The server uses the name to set the character_set_client, character_set_results, and character_set_connection system variables. In effect, the server performs a SET NAMES operation using the character set name.

The effect of this is that you cannot control the client character set by starting mysqld with --character-set-server=utf8. However, some Asian customers prefer the MySQL 4.0 behavior. To make it possible to retain this behavior, we added a mysqld switch, --character-set-client-handshake, which can be turned off with --skip-character-set-client-handshake. If you start mysqld with --skip-character-set-client-handshake, then, when a client connects, it sends to the server the name of the character set that it wants to use. However, the server ignores this request from the client.

By way of example, suppose that your favorite server character set is latin1 (unlikely in a CJK area, but this is the default value). Suppose further that the client uses utf8 because this is what the client's operating system supports. Now, start the server with latin1 as its default character set:

mysqld --character-set-server=latin1

And then start the client with the default character set utf8:

mysql --default-character-set=utf8

The resulting settings can be seen by viewing the output of SHOW VARIABLES:

mysql> SHOW VARIABLES LIKE 'char%';
+--------------------------+----------------------------------------+
| Variable_name            | Value                                  |
+--------------------------+----------------------------------------+
| character_set_client     | utf8                                   |
| character_set_connection | utf8                                   |
| character_set_database   | latin1                                 |
| character_set_filesystem | binary                                 |
| character_set_results    | utf8                                   |
| character_set_server     | latin1                                 |
| character_set_system     | utf8                                   |
| character_sets_dir       | /usr/local/mysql/share/mysql/charsets/ |
+--------------------------+----------------------------------------+

Now stop the client, and stop the server using mysqladmin. Then start the server again, but this time tell it to skip the handshake like so:

mysqld --character-set-server=utf8 --skip-character-set-client-handshake

Start the client with utf8 once again as the default character set, then display the resulting settings:

mysql> SHOW VARIABLES LIKE 'char%';
+--------------------------+----------------------------------------+
| Variable_name            | Value                                  |
+--------------------------+----------------------------------------+
| character_set_client     | latin1                                 |
| character_set_connection | latin1                                 |
| character_set_database   | latin1                                 |
| character_set_filesystem | binary                                 |
| character_set_results    | latin1                                 |
| character_set_server     | latin1                                 |
| character_set_system     | utf8                                   |
| character_sets_dir       | /usr/local/mysql/share/mysql/charsets/ |
+--------------------------+----------------------------------------+

As you can see by comparing the differing results from SHOW VARIABLES, the server ignores the client's initial settings if the --skip-character-set-client-handshake option is used.

A.11.11.

Why do some LIKE and FULLTEXT searches with CJK characters fail?

For LIKE searches, there is a very simple problem with binary string column types such as BINARY and BLOB: we must know where characters end. With multibyte character sets, different characters might have different octet lengths. For example, in utf8, A requires one byte but requires three bytes, as shown here:

+-------------------------+---------------------------+
| OCTET_LENGTH(_utf8 'A') | OCTET_LENGTH(_utf8 'ペ') |
+-------------------------+---------------------------+
|                       1 |                         3 |
+-------------------------+---------------------------+

If we do not know where the first character in a string ends, we do not know where the second character begins, in which case even very simple searches such as LIKE '_A%' fail. The solution is to use a nonbinary string column type defined to have the proper CJK character set. For example: mycol TEXT CHARACTER SET sjis. Alternatively, convert to a CJK character set before comparing.

This is one reason why MySQL cannot permit encodings of nonexistent characters. If it is not strict about rejecting bad input, it has no way of knowing where characters end.

For FULLTEXT searches, we must know where words begin and end. With Western languages, this is rarely a problem because most (if not all) of these use an easy-to-identify word boundary: the space character. However, this is not usually the case with Asian writing. We could use arbitrary halfway measures, like assuming that all Han characters represent words, or (for Japanese) depending on changes from Katakana to Hiragana due to grammatical endings. However, the only sure solution requires a comprehensive word list, which means that we would have to include a dictionary in the server for each Asian language supported. This is simply not feasible.

A.11.12.

How do I know whether character X is available in all character sets?

The majority of simplified Chinese and basic nonhalfwidth Japanese Kana characters appear in all CJK character sets. The following stored procedure accepts a UCS-2 Unicode character, converts it to other character sets, and displays the results in hexadecimal.

DELIMITER //

CREATE PROCEDURE p_convert(ucs2_char CHAR(1) CHARACTER SET ucs2)
BEGIN

CREATE TABLE tj
             (ucs2 CHAR(1) character set ucs2,
              utf8 CHAR(1) character set utf8,
              big5 CHAR(1) character set big5,
              cp932 CHAR(1) character set cp932,
              eucjpms CHAR(1) character set eucjpms,
              euckr CHAR(1) character set euckr,
              gb2312 CHAR(1) character set gb2312,
              gbk CHAR(1) character set gbk,
              sjis CHAR(1) character set sjis,
              ujis CHAR(1) character set ujis);

INSERT INTO tj (ucs2) VALUES (ucs2_char);

UPDATE tj SET utf8=ucs2,
              big5=ucs2,
              cp932=ucs2,
              eucjpms=ucs2,
              euckr=ucs2,
              gb2312=ucs2,
              gbk=ucs2,
              sjis=ucs2,
              ujis=ucs2;

/* If there are conversion problems, UPDATE produces warnings. */

SELECT hex(ucs2) AS ucs2,
       hex(utf8) AS utf8,
       hex(big5) AS big5,
       hex(cp932) AS cp932,
       hex(eucjpms) AS eucjpms,
       hex(euckr) AS euckr,
       hex(gb2312) AS gb2312,
       hex(gbk) AS gbk,
       hex(sjis) AS sjis,
       hex(ujis) AS ujis
FROM tj;

DROP TABLE tj;

END//

DELIMITER ;

The input can be any single ucs2 character, or it can be the code value (hexadecimal representation) of that character. For example, from Unicode's list of ucs2 encodings and names (http://www.unicode.org/Public/UNIDATA/UnicodeData.txt), we know that the Katakana character Pe appears in all CJK character sets, and that its code value is X'30DA'. If we use this value as the argument to p_convert(), the result is as shown here:

mysql> CALL p_convert(X'30DA');
+------+--------+------+-------+---------+-------+--------+------+------+------+
| ucs2 | utf8   | big5 | cp932 | eucjpms | euckr | gb2312 | gbk  | sjis | ujis |
+------+--------+------+-------+---------+-------+--------+------+------+------+
| 30DA | E3839A | C772 | 8379  | A5DA    | ABDA  | A5DA   | A5DA | 8379 | A5DA |
+------+--------+------+-------+---------+-------+--------+------+------+------+

Since none of the column values is 3F (that is, the question mark character, ?), we know that every conversion worked.

A.11.13.

Why do CJK strings sort incorrectly in Unicode? (I)

Sometimes people observe that the result of a utf8_unicode_ci or ucs2_unicode_ci search, or of an ORDER BY sort is not what they think a native would expect. Although we never rule out the possibility that there is a bug, we have found in the past that many people do not correctly read the standard table of weights for the Unicode Collation Algorithm. MySQL uses the tables found under http://www.unicode.org/Public/UCA/:

To handle newer UCA versions, we create new collations. We are very wary about changing ordering of existing collations because that affects indexes, which can bring about situations such as that reported in Bug #16526, illustrated as follows:

mysql> CREATE TABLE tj (s1 CHAR(1) CHARACTER SET utf8 COLLATE utf8_unicode_ci);
Query OK, 0 rows affected (0.05 sec)

mysql> INSERT INTO tj VALUES ('が'),('か');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM tj WHERE s1 = 'か';
+------+
| s1   |
+------+
| が  |
| か  |
+------+

The character in the first result row is not the one that we searched for. Why did MySQL retrieve it? First we look for the Unicode code point value, which is possible by reading the hexadecimal number for the ucs2 version of the characters:

mysql> SELECT s1, HEX(CONVERT(s1 USING ucs2)) FROM tj;
+------+-----------------------------+
| s1   | HEX(CONVERT(s1 USING ucs2)) |
+------+-----------------------------+
| が  | 304C                        |
| か  | 304B                        |
+------+-----------------------------+

Now we search for 304B and 304C in the 4.0.0 allkeys table, and find these lines:

304B  ; [.1E57.0020.000E.304B] # HIRAGANA LETTER KA
304C  ; [.1E57.0020.000E.304B][.0000.0140.0002.3099] # HIRAGANA LETTER GA; QQCM

The official Unicode names (following the # mark) tell us the Japanese syllabary (Hiragana), the informal classification (letter, digit, or punctuation mark), and the Western identifier (KA or GA, which happen to be voiced and unvoiced components of the same letter pair). More importantly, the primary weight (the first hexadecimal number inside the square brackets) is 1E57 on both lines. For comparisons in both searching and sorting, MySQL pays attention to the primary weight only, ignoring all the other numbers. This means that we are sorting and correctly according to the Unicode specification. If we wanted to distinguish them, we'd have to use a non-UCA (Unicode Collation Algorithm) collation (utf8_bin or utf8_general_ci), or to compare the HEX() values, or use ORDER BY CONVERT(s1 USING sjis). Being correct according to Unicode is not enough, of course: the person who submitted the bug was equally correct. To solve this, we need another collation for Japanese according to the JIS X 4061 standard, in which voiced/unvoiced letter pairs like KA/GA are distinguishable for ordering purposes.

A.11.14.

Why do CJK strings sort incorrectly in Unicode? (II)

If you are using Unicode (ucs2 or utf8), and you know what the Unicode sort order is (see Section A.11, “MySQL 5.7 FAQ: MySQL Chinese, Japanese, and Korean Character Sets”), but MySQL still seems to sort your table incorrectly, first verify the character set in the table definition:

mysql> SHOW CREATE TABLE t\G
******************** 1. row ******************
Table: t
Create Table: CREATE TABLE `t` (
`s1` char(1) CHARACTER SET ucs2 DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Since the character set for the column s1 appears to be correct (ucs2), check what information the INFORMATION_SCHEMA.COLUMNS table can provide about this column:

mysql> SELECT COLUMN_NAME, CHARACTER_SET_NAME, COLLATION_NAME
       FROM INFORMATION_SCHEMA.COLUMNS
       WHERE COLUMN_NAME = 's1'
       AND TABLE_NAME = 't';
+-------------+--------------------+-----------------+
| COLUMN_NAME | CHARACTER_SET_NAME | COLLATION_NAME  |
+-------------+--------------------+-----------------+
| s1          | ucs2               | ucs2_general_ci |
+-------------+--------------------+-----------------+

(See Section 22.4, “The INFORMATION_SCHEMA COLUMNS Table”, for more information.)

You can see that the collation is ucs2_general_ci instead of ucs2_unicode_ci. The reason why this is so can be found using SHOW CHARACTER SET, as shown here:

mysql> SHOW CHARSET LIKE 'ucs2%';
+---------+---------------+-------------------+--------+
| Charset | Description   | Default collation | Maxlen |
+---------+---------------+-------------------+--------+
| ucs2    | UCS-2 Unicode | ucs2_general_ci   |      2 |
+---------+---------------+-------------------+--------+

For ucs2 and utf8, the default collation is general. To specify a Unicode UCA collation, use COLLATE ucs2_unicode_ci, as shown in the preceding item.

A.11.15.

Why are my supplementary characters rejected by MySQL?

Supplementary characters lie outside the Unicode Basic Multilingual Plane / Plane 0. BMP characters have code point values between U+0000 and U+FFFF. Supplementary characters have code point values between U+10000 and U+10FFFF.

To store supplementary characters, you must use a character set that permits them:

  • The utf8 and ucs2 character sets support BMP characters only.

    The utf8 character set permits only UTF-8 characters that take up to three bytes. This has led to reports such as that found in Bug #12600, which we rejected as not a bug. With utf8, MySQL must truncate an input string when it encounters bytes that it does no understand. Otherwise, it is unknown how long the bad multibyte character is.

    One possible workaround is to use ucs2 instead of utf8, in which case the bad characters are changed to question marks. However, no truncation takes place. You can also change the data type to BLOB or BINARY, which perform no validity checking.

  • The utf8mb4, utf16, utf16le, and utf32 character sets support BMP characters, as well as supplementary characters outside the BMP.

A.11.16.

Should CJK be CJKV?

No. The term CJKV (Chinese Japanese Korean Vietnamese) refers to Vietnamese character sets which contain Han (originally Chinese) characters. MySQL supports the modern Vietnamese script with Western characters, but does not support the old Vietnamese script using Han characters.

As of MySQL 5.6, there are Vietnamese collations for Unicode character sets, as described in Section 11.1.10.1, “Unicode Character Sets”.

A.11.17.

Does MySQL permit CJK characters to be used in database and table names?

Yes.

A.11.18.

Where can I find translations of the MySQL Manual into Chinese, Japanese, and Korean?

The Japanese translation of the MySQL 5.6 manual can be downloaded from http://dev.mysql.com/doc/.

A.11.19.

Where can I get help with CJK and related issues in MySQL?

The following resources are available:


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