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https://dev.mysql.com/doc/refman/8.0/en/optimization-indexes.html
Although it can be tempting to create an indexes for every possible column used in a query, unnecessary indexes waste space and waste time for MySQL to determine which indexes to use. The best way to improve the performance of SELECT operations is ...
https://dev.mysql.com/doc/refman/8.0/en/optimize-benchmarking.html
To measure performance, consider the following factors: Whether you are measuring the speed of a single operation on a quiet system, or how a set of operations (a “workload”) works over a period of time. Benchmarks are typically long-running ...
https://dev.mysql.com/doc/refman/8.0/en/platform-support.html
MySQL platform support evolves over time; please refer to https://www.mysql.com/support/supportedplatforms/database.html for the latest updates.
https://dev.mysql.com/doc/refman/8.0/en/replication-features-differing-tables.html
A column's default value is determined by a number of factors, including its type, whether it is defined with a DEFAULT option, whether it is declared as NULL, and the server SQL mode in effect at the time of its creation; for more information, see ... Source and target tables for replication do not have to be ...
https://dev.mysql.com/doc/refman/8.0/en/scalar-subqueries.html
In MySQL 8.0.19 and later, the preceding query can also be written like this, using TABLE: SELECT (TABLE t2) FROM t1; A scalar subquery can be part of an expression, but remember the parentheses, even if the subquery is an operand that provides an ... In its simplest form, a subquery is a scalar subquery that returns a single ...
https://dev.mysql.com/doc/refman/8.0/en/server-configuration-defaults.html
The MySQL server has many operating parameters, which you can change at server startup using command-line options or configuration files (option files). For general instructions on setting parameters at startup or runtime, see Section 7.1.7, ...
https://dev.mysql.com/doc/refman/8.0/en/sys-execute-prepared-stmt.html
Thus, this procedure is useful primarily for executing dynamic statements on a one-time basis. Example mysql> CALL sys.execute_prepared_stmt('SELECT COUNT(*) FROM mysql.user'); +----------+ | COUNT(*) | +----------+ | 15 | +----------+ . Given an ...
https://dev.mysql.com/doc/refman/8.0/en/sys-schema-views.html
The sys schema contains many views that summarize Performance Schema tables in various ways. Most of these views come in pairs, such that one member of the pair has the same name as the other member, plus a x$ prefix. The view with the x$ prefix ...
https://dev.mysql.com/doc/refman/8.0/en/view-restrictions.html
In this case, the view is stored in a temporary table and thus you are not really selecting from the table in a subquery and modifying it at the same time. (This is another reason you might wish to force MySQL to use the temptable algorithm by ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-events-transactions-current-table.html
For example: mysql> SELECT * FROM performance_schema.events_transactions_current LIMIT 1\G *************************** 1. The TIMER_START and TIMER_END values indicate when event timing started and ended. If an event has not finished, TIMER_END is ...The table stores one row per thread showing the current status of the thread's most recent monitored transaction event, so there is no system variable for configuring the table ...