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https://dev.mysql.com/doc/refman/8.0/en/monitor-mysql-memory-use.html
Instruments can be enabled by updating the ENABLED column of the Performance Schema setup_instruments table. To view available MySQL memory instruments, query the Performance Schema setup_instruments table. After restarting the server, the ENABLED ... The following example demonstrates how to use Performance Schema and sys schema to monitor MySQL memory ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-importing-data.html
You may also wish to do this when performing bulk DELETE or UPDATE operations on NDB Cluster tables. If a data import operation does not complete successfully, for whatever reason, you should be prepared to perform any necessary cleanup including ...
https://dev.mysql.com/doc/refman/8.0/en/optimize-character.html
The GROUP BY and ORDER BY clauses can generate temporary tables, and these temporary tables can use the MEMORY storage engine if the original table does not contain any BLOB columns. If a table contains string columns such as name and address, but ... For character and string columns, follow these guidelines: Use binary collation order for fast comparison and sort operations, when you do not need language-specific collation ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-timing.html
For example, the standard gettimeofday() function can take hundreds of cycles, which is an unacceptable overhead for data gathering that may occur thousands or millions of times per second. Performance Schema Timer Representation in Events Rows in ... Events are collected by means of instrumentation added to the server source ...
https://dev.mysql.com/doc/refman/8.0/en/replication-features-reserved-words.html
For example, a table column named rank on a MySQL 5.7 source that is replicating to a MySQL 8.0 replica could cause a problem because RANK is a reserved word beginning in MySQL 8.0. Replication can fail in such cases with Error 1064 You have an ...
https://dev.mysql.com/doc/refman/8.0/en/secure-client-programming.html
If an application generates a query such as SELECT * FROM table WHERE ID=234 when a user enters the value 234, the user can enter the value 234 OR 1=1 to cause the application to generate the query SELECT * FROM table WHERE ID=234 OR 1=1. As a ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-errors.html
In MySQL 8.0.19 and later, all of the errors described in this section also apply when using TABLE in subqueries. Incorrect number of rows from subquery: ERROR 1242 (ER_SUBSELECT_NO_1_ROW) SQLSTATE = 21000 Message = "Subquery returns more than 1 ...
https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html
mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','GMT','MET'); -> '2004-01-01 13:00:00' mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','+00:00','+10:00'); -> '2004-01-01 22:00:00' Note To use named time zones such as 'MET' or 'Europe/Amsterdam', the ... This section describes the functions that can be used to manipulate temporal ...
https://dev.mysql.com/doc/refman/8.0/en/descending-indexes.html
For InnoDB full-text search, this means that the index required on the FTS_DOC_ID column of the indexed table cannot be defined as a descending index. MySQL supports descending indexes: DESC in an index definition is no longer ignored but causes ...
https://dev.mysql.com/doc/refman/8.0/en/loadable-function-reference.html
The following table lists each function that is loadable at runtime and provides a short description of each one. For a table listing built-in functions and operators, see Section 14.1, “Built-In Function and Operator Reference” For general ...