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https://dev.mysql.com/doc/refman/8.0/en/show-columns.html
on update CURRENT_TIMESTAMP for TIMESTAMP or DATETIME columns that have the ON UPDATE CURRENT_TIMESTAMP attribute. These two statements are equivalent: SHOW COLUMNS FROM mytable FROM mydb; SHOW COLUMNS FROM mydb.mytable; The optional EXTENDED ...
https://dev.mysql.com/doc/refman/8.0/en/silent-column-changes.html
See Section 10.4.7, “Limits on Table Column Count and Row Size”. Trailing spaces are automatically deleted from ENUM and SET member values when the table is created. If strict SQL mode is not enabled, a VARCHAR column with a length specification ... In some cases, MySQL silently changes column specifications from those given in a CREATE TABLE or ALTER TABLE ...
https://dev.mysql.com/doc/refman/8.0/en/static-format.html
Of the three MyISAM storage formats, static format is the simplest and most secure (least subject to corruption). In this case, myisamchk can easily determine where each row starts and ends, so it can usually reclaim all rows except the partially ...
https://dev.mysql.com/doc/refman/8.0/en/structured-system-variables.html
The following example starts the server with three different key caches having sizes in a 3:1:1 ratio: $> mysqld --key_buffer_size=6M \ --hot_cache.key_buffer_size=2M \ --cold_cache.key_buffer_size=2M Structured variable values may be set and ... A ...
https://dev.mysql.com/doc/refman/8.0/en/sys-schema-usage.html
For additional information about the differences between non-x$ and x$ views, see Section 30.4.3, “sys Schema Views”. For example, to examine the definitions of the session view and format_bytes() function, use these statements: mysql> SHOW ...
https://dev.mysql.com/doc/refman/8.0/en/sys-sys-get-config.html
If sys_get_config() returns the default value and that value is NULL, it is expected that the caller is able to handle NULL for the given configuration option. By convention, routines that call sys_get_config() first check whether the corresponding ... Given a configuration option name, returns the option value from the sys_config table, or the provided default value (which may be NULL) if the option does not exist in the ...
https://dev.mysql.com/doc/refman/8.0/en/table-corruption.html
If you have started mysqld with the myisam_recover_options system variable set, MySQL automatically checks and tries to repair MyISAM tables if they are marked as 'not closed properly' or 'crashed'. If you get a lot of these errors, without mysqld ...If this happens, MySQL writes an entry in the hostname.err file 'Warning: Checking table ...' which is followed by Warning: Repairing table if the table needs to be ...
https://dev.mysql.com/doc/refman/8.0/en/table-scan-avoidance.html
This is common for tables with fewer than 10 rows and a short row length. You are comparing indexed columns with constant values and MySQL has calculated (based on the index tree) that the constants cover too large a part of the table and that a ...
https://dev.mysql.com/doc/refman/8.0/en/traceable-statements.html
Statements which are traceable are listed here: SELECT INSERT REPLACE UPDATE DELETE EXPLAIN with any of the preceding statements SET DO DECLARE, CASE, IF, and RETURN as used in stored routines CALL Tracing is supported for both INSERT and REPLACE ...For statements which are prepared and executed in separate steps, preparation and execution are traced ...
https://dev.mysql.com/doc/refman/8.0/en/triggers.html
A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table. Some uses for triggers are to perform checks of values to be inserted into a table or to perform calculations on ...A trigger can be set to activate either before or after the trigger ...