https://dev.mysql.com/mysql-tips.html
Connection id: 1 Current database: test Query OK, 1 row affected (1.30 sec) mysql> SELECT * FROM t; +------+ | a | +------+ | NULL | +------+ 1 row in set (0.05 sec) The @a user variable has been lost with the connection, and after the reconnection ... This section provides information about techniques for more effective use of mysql and about mysql operational ...
https://dev.mysql.com/mysqlslap.html
shell> mysqlslap --delimiter=";" --number-of-queries=10 --query="use test;insert into t values(null)" --only-print Do not connect to databases. mysqlslap is a diagnostic program designed to emulate client load for a MySQL server and to report the ...
https://dev.mysql.com/order-by-optimization.html
In MySQL 8.0, that no longer occurs, so specifying ORDER BY NULL at the end to suppress implicit sorting (as was done previously) is no longer necessary. This section describes when MySQL can use an index to satisfy an ORDER BY clause, the filesort ...
https://dev.mysql.com/pam-pluggable-authentication.html
Note PAM pluggable authentication is an extension included in MySQL Enterprise Edition, a commercial product. MySQL Enterprise Edition supports an authentication method that enables MySQL Server to use PAM (Pluggable Authentication Modules) to ...
https://dev.mysql.com/partitioning.html
See Section 25.20, “The INFORMATION_SCHEMA PARTITIONS Table”, for more information; for some examples of queries against this table, see Section 23.2.7, “How MySQL Partitioning Handles NULL”. Note Table partitioning differs from partitioning ...
https://dev.mysql.com/performance-schema-connection-tables.html
The Performance Schema also counts internal threads and threads for user sessions that failed to authenticate, using rows with USER and HOST column values of NULL. When a client connects to the MySQL server, it does so under a particular user name ...
https://dev.mysql.com/performance-schema-consumer-filtering.html
Conversely, you can get detailed statements in events_statements_current without digests (the DIGEST and DIGEST_TEXT columns will be NULL). To enable or disable a consumer, set its ENABLED value to YES or NO. If you disable a consumer, the server ...
https://dev.mysql.com/performance-schema-pre-filtering.html
Generally, the effect is to reset the summary columns to 0 or NULL, not to remove rows. Pre-filtering is done by the Performance Schema and has a global effect that applies to all users. Pre-filtering can be applied to either the producer or ...
https://dev.mysql.com/performance-schema-queries.html
Pre-filtering limits which event information is collected and is independent of any particular user. By contrast, post-filtering is performed by individual users through the use of queries with appropriate WHERE clauses that restrict what event ...
https://dev.mysql.com/performance-schema-restrictions.html
If the values in this table for a given timer name are NULL, that timer is not supported on your platform. The Performance Schema avoids using mutexes to collect or produce data, so there are no guarantees of consistency and results can sometimes ...
