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https://dev.mysql.com/doc/refman/5.7/en/delete-optimization.html
The time required to delete individual rows in a MyISAM table is exactly proportional to the number of indexes. To delete all rows from a MyISAM table, TRUNCATE TABLE tbl_name is faster than DELETE FROM tbl_name. Truncate operations are not ...To ...
https://dev.mysql.com/doc/refman/5.7/en/drop-database.html
DROP {DATABASE | SCHEMA} [IF EXISTS] db_name DROP DATABASE drops all tables in the database and deletes the database. Dropping a database does not remove any TEMPORARY tables that were created in that database. TEMPORARY tables are automatically ...
https://dev.mysql.com/doc/refman/5.7/en/engine-condition-pushdown-optimization.html
Joins are not directly supported; conditions involving multiple tables are pushed separately where possible. This optimization improves the efficiency of direct comparisons between a nonindexed column and a constant. In such cases, the condition is ...
https://dev.mysql.com/doc/refman/5.7/en/environment-variables.html
This section lists environment variables that are used directly or indirectly by MySQL. Most of these can also be found in other places in this manual. Options on the command line take precedence over values specified in option files and ...
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 ...