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https://dev.mysql.com/doc/refman/8.0/en/all-subqueries.html
The expression is TRUE if table t2 contains (-5,0,+5) because 10 is greater than all three values in t2. The expression is FALSE if table t2 contains (12,6,NULL,-100) because there is a single value 12 in table t2 that is greater than 10. The ...
https://dev.mysql.com/doc/refman/8.0/en/any-in-some-subqueries.html
The expression is TRUE if table t2 contains (21,14,7) because there is a value 7 in t2 that is less than 10. The expression is FALSE if table t2 contains (20,10), or if table t2 is empty. The expression is unknown (that is, NULL) if table t2 ...
https://dev.mysql.com/doc/refman/8.0/en/correlated-subqueries.html
A correlated subquery is a subquery that contains a reference to a table that also appears in the outer query. For example: SELECT * FROM t1 WHERE column1 = ANY (SELECT column1 FROM t2 WHERE t2.column2 = t1.column2); Notice that the subquery ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-buffer-pool-resize.html
You can configure InnoDB buffer pool size offline or while the server is running. For additional information about configuring buffer pool size online, see Configuring InnoDB Buffer Pool Size Online. When increasing or decreasing ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-information-schema-buffer-pool-tables.html
The InnoDB INFORMATION_SCHEMA buffer pool tables provide buffer pool status information and metadata about the pages within the InnoDB buffer pool. The InnoDB INFORMATION_SCHEMA buffer pool tables include those listed below: mysql> SHOW TABLES FROM ...
https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html
If you specify an ON DUPLICATE KEY UPDATE clause and a row to be inserted would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row occurs. If column b is also unique, the INSERT is equivalent to this UPDATE statement ...
https://dev.mysql.com/doc/refman/8.0/en/where-optimization.html
This section discusses optimizations that can be made for processing WHERE clauses. The examples use SELECT statements, but the same optimizations apply for WHERE clauses in DELETE and UPDATE statements. Note Because work on the MySQL optimizer is ...
https://dev.mysql.com/doc/refman/8.0/en/entering-queries.html
Make sure that you are connected to the server, as discussed in the previous section. Doing so does not in itself select any database to work with, but that is okay. At this point, it is more important to find out a little about how to issue ...
https://dev.mysql.com/doc/refman/8.0/en/exists-and-not-exists-subqueries.html
If a subquery returns any rows at all, EXISTS subquery is TRUE, and NOT EXISTS subquery is FALSE. For example: SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2); Traditionally, an EXISTS subquery starts with SELECT *, but it could begin with ...
https://dev.mysql.com/doc/refman/8.0/en/hash-joins.html
By default, MySQL (8.0.18 and later) employs hash joins whenever possible. It is possible to control whether hash joins are employed using one of the BNL and NO_BNL optimizer hints, or by setting block_nested_loop=on or block_nested_loop=off as ...