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https://dev.mysql.com/doc/refman/5.7/en/sys-sys-get-config.html
However, this should not be done inside a loop (for example, for each row in a result set) because for repeated calls where the assignment is needed only in the first iteration, using IFNULL(...) is expected to be significantly slower than using an ... 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/5.7/en/sys-table-exists.html
This is an OUT parameter, so it must be a variable into which the table type can be stored. Tests whether a given table exists as a regular table, a TEMPORARY table, or a view. If both a temporary and a permanent table exist with the given name, ...
https://dev.mysql.com/doc/refman/5.7/en/sys-version-major.html
This function returns the major version of the MySQL server. Example mysql> SELECT VERSION(), sys.version_major(); +------------------+---------------------+ | VERSION() | sys.version_major() | +------------------+---------------------+ | ...
https://dev.mysql.com/doc/refman/5.7/en/sys-version-minor.html
This function returns the minor version of the MySQL server. Example mysql> SELECT VERSION(), sys.version_minor(); +------------------+---------------------+ | VERSION() | sys.version_minor() | +------------------+---------------------+ | ...
https://dev.mysql.com/doc/refman/5.7/en/sys-version-patch.html
This function returns the patch release version of the MySQL server. Example mysql> SELECT VERSION(), sys.version_patch(); +------------------+---------------------+ | VERSION() | sys.version_patch() | +------------------+---------------------+ | ...
https://dev.mysql.com/doc/refman/5.7/en/temporary-table-problems.html
Temporary tables created with CREATE TEMPORARY TABLE have the following limitations: TEMPORARY tables are supported only by the InnoDB, MEMORY, MyISAM, and MERGE storage engines. Use ALTER TABLE instead: ALTER TABLE old_name RENAME new_name; You ...
https://dev.mysql.com/doc/refman/5.7/en/thread-pool-elements.html
To identify them, use this query: SELECT * FROM performance_schema.setup_instruments WHERE NAME LIKE '%thread_pool%'; For more information, see Chapter 25, MySQL Performance Schema. MySQL Enterprise Thread Pool comprises these elements: A plugin ...
https://dev.mysql.com/doc/refman/5.7/en/timezone-problems.html
This should be done for the environment in which the server runs (for example, in mysqld_safe or mysql.server). If you have a problem with SELECT NOW() returning values in UTC and not your local time, you have to tell the server your current time ...
https://dev.mysql.com/doc/refman/5.7/en/truncate-table.html
This is true even for MyISAM and InnoDB, which normally do not reuse sequence values. Logically, TRUNCATE TABLE is similar to a DELETE statement that deletes all rows, or a sequence of DROP TABLE and CREATE TABLE statements. To achieve high ...
https://dev.mysql.com/doc/refman/5.7/en/update-optimization.html
If you do this often, it is very important to use OPTIMIZE TABLE occasionally. An update statement is optimized like a SELECT query with the additional overhead of a write. The speed of the write depends on the amount of data being updated and the ...