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https://dev.mysql.com/doc/refman/8.0/en/server-option-variable-reference.html
The following table lists all command-line options, system variables, and status variables applicable within mysqld. The table lists command-line options (Cmd-line), options valid in configuration files (Option file), server system variables ...If ...
https://dev.mysql.com/doc/refman/8.0/en/server-shutdown.html
For additional information about thread termination, see Section 15.7.8.4, “KILL Statement”, in particular for the instructions about killed REPAIR TABLE or OPTIMIZE TABLE operations on MyISAM tables. If a thread is updating a nontransactional ... The server shutdown process takes place as follows: The shutdown process is ...
https://dev.mysql.com/doc/refman/8.0/en/show-triggers.html
SHOW TRIGGERS [{FROM | IN} db_name] [LIKE 'pattern' | WHERE expr] SHOW TRIGGERS lists the triggers currently defined for tables in a database (the default database unless a FROM clause is given). This statement returns results only for databases ...
https://dev.mysql.com/doc/refman/8.0/en/subqueries.html
They provide alternative ways to perform operations that would otherwise require complex joins and unions. Beginning with MySQL 8.0.19, TABLE and VALUES statements can be used in subqueries. For information about how the optimizer handles ...All ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-materialization.html
Materialization speeds up query execution by generating a subquery result as a temporary table, normally in memory. The first time MySQL needs the subquery result, it materializes that result into a temporary table. Any subsequent time the result is ... The optimizer uses materialization to enable more efficient subquery ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-optimization-with-exists.html
row *************************** id: 2 select_type: DEPENDENT SUBQUERY table: t2 type: ref_or_null possible_keys: maybe_null_key key: maybe_null_key key_len: 5 ref: func rows: 2 Extra: Using where; Using index ... Triggered equalities can be used by ... Certain optimizations are applicable to comparisons that use the IN (or =ANY) operator to test subquery ...
https://dev.mysql.com/doc/refman/8.0/en/sys-metrics.html
The metric type determines the source from which the name is taken: For global status variables: The VARIABLE_NAME column of the global_status table For InnoDB metrics: The NAME column of the INNODB_METRICS table For other metrics: A view-provided ... This view summarizes MySQL server metrics to show variable names, values, types, and whether they are ...
https://dev.mysql.com/doc/refman/8.0/en/sys-sys-get-config.html
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 table. If so, the routine uses the variable value without reading the ...If ...
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 ...For example, rows can be inserted by INSERT or LOAD DATA statements, and an insert trigger activates for each inserted ...
https://dev.mysql.com/doc/refman/8.0/en/constraint-foreign-key.html
MySQL supports ON UPDATE and ON DELETE foreign key references in CREATE TABLE and ALTER TABLE statements. Foreign keys let you cross-reference related data across tables, and foreign key constraints help keep this spread-out data consistent. MySQL ...The available referential actions are RESTRICT, CASCADE, SET NULL, and NO ACTION (the ...