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https://dev.mysql.com/doc/refman/8.0/en/subquery-materialization.html
The optimizer uses materialization to enable more efficient subquery processing. 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 ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-restrictions.html
In general, you cannot modify a table and select from the same table in a subquery. For example, this limitation applies to statements of the following forms: DELETE FROM t WHERE ... FROM t ...); Exception: The preceding prohibition does not apply ...
https://dev.mysql.com/doc/refman/8.0/en/sys-diagnostics.html
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 variable. That is a restricted operation, so the ...
https://dev.mysql.com/doc/refman/8.0/en/sys-host-summary-by-file-io.html
By default, rows are sorted by descending total file I/O latency. The host_summary_by_file_io and x$host_summary_by_file_io views have these columns: host The host from which the client connected. Rows for which the HOST column in the underlying ...
https://dev.mysql.com/doc/refman/8.0/en/sys-schema-object-index.html
The following tables list sys schema objects and provide a short description of each one.
https://dev.mysql.com/doc/refman/8.0/en/sys-user-summary-by-file-io.html
By default, rows are sorted by descending total file I/O latency. The user_summary_by_file_io and x$user_summary_by_file_io views have these columns: user The client user name. Rows for which the USER column in the underlying Performance Schema ...
https://dev.mysql.com/doc/refman/8.0/en/thread-information.html
To ascertain what your MySQL server is doing, it can be helpful to examine the process list, which indicates the operations currently being performed by the set of threads executing within the server. row *************************** Id: 5 User: ...
https://dev.mysql.com/doc/refman/8.0/en/update.html
UPDATE is a DML statement that modifies rows in a table. An UPDATE statement can start with a WITH clause to define common table expressions accessible within the UPDATE. Single-table syntax: UPDATE [LOW_PRIORITY] [IGNORE] table_reference SET ...
https://dev.mysql.com/doc/refman/8.0/en/user-variables.html
You can store a value in a user-defined variable in one statement and refer to it later in another statement. This enables you to pass values from one statement to another. User variables are written as @var_name, where the variable name var_name ...
https://dev.mysql.com/doc/refman/8.0/en/using-date.html
You should use this format in UPDATE expressions and in the WHERE clause of SELECT statements. For example: SELECT * FROM t1 WHERE date >= '2003-05-05'; As a convenience, MySQL automatically converts a date to a number if the date is used in numeric ...