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https://dev.mysql.com/doc/refman/5.7/en/any-in-some-subqueries.html
The expression is TRUE if table t2 contains (21,14,7) because there is a value 7 in t2 that is less than 10. The expression is FALSE if table t2 contains (20,10), or if table t2 is empty. The expression is unknown (that is, NULL) if table t2 ...When ...
https://dev.mysql.com/doc/refman/5.7/en/blob.html
For example, if a table contains 'a', an attempt to store 'a ' causes a duplicate-key error. This is in contrast to all other data types, for which storage is allocated once per column when the table is opened. A BLOB is a binary large object that ...
https://dev.mysql.com/doc/refman/5.7/en/charset-cp932.html
The table shown at https://msdn.microsoft.com/en-us/goglobal/cc305152.aspx provides information about the Unicode values of cp932 characters. For cp932 table entries with characters under which a four-digit number appears, the number represents the ... Why is cp932 needed? In MySQL, the sjis character set corresponds to the Shift_JIS character set defined by IANA, which supports JIS X0201 and JIS X0208 ...
https://dev.mysql.com/doc/refman/5.7/en/controlling-query-plan-evaluation.html
For join queries, the number of possible plans investigated by the MySQL optimizer grows exponentially with the number of tables referenced in a query. For small numbers of tables (typically less than 7 to 10) this is not a problem. The behavior of ... The task of the query optimizer is to find an optimal plan for executing an SQL ...
https://dev.mysql.com/doc/refman/5.7/en/data-masking-usage.html
Suppose that a customer table containing customer records has these columns: id: Customer ID number. Creating Views that Display Masked Data If masked data from a table is used for multiple queries, it may be convenient to define a view that ...
https://dev.mysql.com/doc/refman/5.7/en/date-and-time-type-syntax.html
For example: CREATE TABLE t1 (t TIME(3), dt DATETIME(6), ts TIMESTAMP(0)); The fsp value, if given, must be in the range 0 to 6. (This differs from the standard SQL default of 6, for compatibility with previous MySQL versions.) Any TIMESTAMP or ...
https://dev.mysql.com/doc/refman/5.7/en/delete-optimization.html
The time required to delete individual rows in a MyISAM table is exactly proportional to the number of indexes. To delete all rows from a MyISAM table, TRUNCATE TABLE tbl_name is faster than DELETE FROM tbl_name. Truncate operations are not ...To ...
https://dev.mysql.com/doc/refman/5.7/en/drop-database.html
DROP {DATABASE | SCHEMA} [IF EXISTS] db_name DROP DATABASE drops all tables in the database and deletes the database. Dropping a database does not remove any TEMPORARY tables that were created in that database. TEMPORARY tables are automatically ...
https://dev.mysql.com/doc/refman/5.7/en/engine-condition-pushdown-optimization.html
Joins are not directly supported; conditions involving multiple tables are pushed separately where possible. This optimization improves the efficiency of direct comparisons between a nonindexed column and a constant. In such cases, the condition is ...
https://dev.mysql.com/doc/refman/5.7/en/environment-variables.html
This section lists environment variables that are used directly or indirectly by MySQL. Most of these can also be found in other places in this manual. Options on the command line take precedence over values specified in option files and ...