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https://dev.mysql.com/doc/refman/5.7/en/estimating-performance.html
For small tables, you can usually find a row in one disk seek (because the index is probably cached). For bigger tables, you can estimate that, using B-tree indexes, you need this many seeks to find a row: log(row_count) / log(index_block_length / 3 ... In most cases, you can estimate query performance by counting disk ...
https://dev.mysql.com/doc/refman/5.7/en/faqs-general.html
For the syntax required to perform multiple-table updates, see Section 13.2.11, “UPDATE Statement”; for that required to perform multiple-table deletes, see Section 13.2.2, “DELETE Statement”. A multiple-table insert can be accomplished ...
https://dev.mysql.com/doc/refman/5.7/en/flow-control-functions.html
The default return type of IF() (which may matter when it is stored into a temporary table) is calculated as follows: If expr2 or expr3 produce a string, the result is a string. The second syntax returns the result for the first condition that is ...
https://dev.mysql.com/doc/refman/5.7/en/group-by-modifiers.html
To work around the restriction that prevents using ROLLUP with ORDER BY and achieve a specific sort order of grouped results, generate the grouped result set as a derived table and apply ORDER BY to it. The GROUP BY clause permits a WITH ROLLUP ...
https://dev.mysql.com/doc/refman/5.7/en/group-replication-configuring-instances.html
For more information, see Section 4.4.7, “mysql_upgrade — Check and Upgrade MySQL Tables”. server_id=1 gtid_mode=ON enforce_gtid_consistency=ON master_info_repository=TABLE relay_log_info_repository=TABLE binlog_checksum=NONE ... This section ...
https://dev.mysql.com/doc/refman/5.7/en/help.html
Its proper operation requires that the help tables in the mysql database be initialized with help topic information (see Section 5.1.14, “Server-Side Help Support”). The HELP statement searches the help tables for the given search string and ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-deadlock-example.html
First, client A creates a table containing one row, and then begins a transaction. Finally, client A also attempts to delete the row from the table: mysql> DELETE FROM t WHERE i = 1; Deadlock occurs here because client A needs an X lock to delete ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-file-format.html
It supports the COMPACT and REDUNDANT row formats for InnoDB tables. The features associated with COMPRESSED and DYNAMIC row formats include compressed tables, efficient storage of off-page columns, and index key prefixes up to 3072 bytes ... As ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-performance-midpoint_insertion.html
The goal is to make sure that frequently accessed (“hot”) pages remain in the buffer pool, even as read-ahead and full table scans bring in new blocks that might or might not be accessed afterward. You can control the insertion point in the LRU ... Rather than using a strict LRU algorithm, InnoDB uses a technique to minimize the amount of data that is brought into the buffer pool and never accessed ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-transaction-isolation-levels.html
InnoDB offers all four transaction isolation levels described by the SQL:1992 standard: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, and SERIALIZABLE. You can enforce a high degree of consistency with the default REPEATABLE READ level, for ...