Search Results
https://dev.mysql.com/doc/refman/8.4/en/prepare.html
A parameter that is an output operand of any of CASE, COALESCE, IF, IFNULL, or NULLIF has the same derived type as the aggregated type of the operator's other output operands. If all output operands of any of CASE, COALESCE, IF, IFNULL, or NULLIF ...
https://dev.mysql.com/doc/refman/8.4/en/primary-key-optimization.html
Query performance benefits from the NOT NULL optimization, because it cannot include any NULL values. The primary key for a table represents the column or set of columns that you use in your most vital queries. With the InnoDB storage engine, the ...
https://dev.mysql.com/doc/refman/8.4/en/processlist-access.html
db is the default database for the thread, or NULL if none has been selected. Info indicates the statement the thread is executing, or NULL if it is executing no statement. The following discussion enumerates the sources of process information, the ...
https://dev.mysql.com/doc/refman/8.4/en/rewriter-query-rewrite-plugin-reference.html
If no error occurs when the rules table is loaded into memory, the plugin sets the message column to NULL. A non-NULL value indicates an error and the column contents are the error message. Users communicate with the plugin by modifying the set of ...
https://dev.mysql.com/doc/refman/8.4/en/sys-diagnostics.html
Use NULL to collect data for the default of 60 seconds. Creates a report of the current server status for diagnostic purposes. This procedure disables binary logging during its execution by manipulating the session value of the sql_log_bin system ...
https://dev.mysql.com/doc/refman/8.4/en/sys-processlist.html
db The default database for the thread, or NULL if there is none. current_statement The statement the thread is executing, or NULL if it is not executing any statement. The MySQL process list indicates the operations currently being performed by ...
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-is-consumer-enabled.html
Returns YES or NO to indicate whether a given Performance Schema consumer is enabled, or NULL if the argument is NULL. If the argument is not a valid consumer name, an error occurs. This function accounts for the consumer hierarchy, so a consumer ...
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-is-thread-instrumented.html
Returns YES or NO to indicate whether Performance Schema instrumentation for a given connection ID is enabled, UNKNOWN if the ID is unknown, or NULL if the ID is NULL. This is a value of the type given in the PROCESSLIST_ID column of the ...
https://dev.mysql.com/doc/refman/8.4/en/user-variables.html
User variables can be assigned a value from a limited set of data types: integer, decimal, floating-point, binary or nonbinary string, or NULL value. If you refer to a variable that has not been initialized, it has a value of NULL and a type of ...
https://dev.mysql.com/doc/refman/8.4/en/using-date.html
When a '0000-00-00' date is used through Connector/ODBC, it is automatically converted to NULL because ODBC cannot handle that kind of date. MySQL permits you to store a “zero” value of '0000-00-00' as a “dummy date.” This is in some cases ...You should use this format in UPDATE expressions and in the WHERE clause of SELECT ...