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https://dev.mysql.com/doc/refman/8.4/en/handler-scope.html
For example, a statement could generate multiple warnings with different error codes, for each of which an error-specific handler exists. However, SQLSTATE handlers take precedence over SQLEXCEPTION handlers, so if the table t is nonexistent, the ...
https://dev.mysql.com/doc/refman/8.4/en/hash-joins.html
row *************************** EXPLAIN: -> Hash semijoin (t2.c2 = t1.c1) (cost=0.70 rows=1) -> Table scan on t1 (cost=0.35 rows=1) -> Hash -> Table scan on t2 (cost=0.35 rows=1) Antijoin: mysql> EXPLAIN FORMAT=TREE SELECT * FROM t2 -> WHERE NOT ...
https://dev.mysql.com/doc/refman/8.4/en/help.html
Example: HELP 'status' Yields: Many help items for your request exist. HELP 'search_string' The HELP statement returns online information from the MySQL Reference Manual. Its proper operation requires that the help tables in the mysql database be ...
https://dev.mysql.com/doc/refman/8.4/en/host-cache.html
The MySQL server maintains an in-memory host cache that contains information about clients: IP address, host name, and error information. The Performance Schema host_cache table exposes the contents of the host cache so that it can be examined ...
https://dev.mysql.com/doc/refman/8.4/en/identifiers.html
It is also recommended that you do not use column names that begin with !hidden! to ensure that new names do not collide with names used by existing hidden columns for functional indexes. Certain objects within MySQL, including database, table, ...
https://dev.mysql.com/doc/refman/8.4/en/implicit-commit.html
For example, if you use CREATE TEMPORARY TABLE and then roll back the transaction, the table remains in existence. The statements listed in this section (and any synonyms for them) implicitly end any transaction active in the current session, as if ...
https://dev.mysql.com/doc/refman/8.4/en/import-table.html
Given those file names, the copy commands look like this: $> cd export_basedir/data/hr $> cp employees_125.sdi /tmp/export $> cp managers_238.sdi /tmp/export $> cp employees.{MYD,MYI} /tmp/export $> cp managers.{MYD,MYI} /tmp/export Unlock the ...
https://dev.mysql.com/doc/refman/8.4/en/index-condition-pushdown-optimization.html
(For information about triggered conditions, see Section 10.2.2.3, “Optimizing Subqueries with the EXISTS Strategy”.) Conditions cannot be pushed down to derived tables containing references to system variables. Index Condition Pushdown (ICP) ...
https://dev.mysql.com/doc/refman/8.4/en/index-page-merge-threshold.html
If the “page-full” percentage for an index page falls below the MERGE_THRESHOLD value when a row is deleted or when a row is shortened by an UPDATE operation, InnoDB attempts to merge the index page with a neighboring index page. The default ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-cmp-per-index-table.html
Compressed InnoDB pages are uncompressed whenever compression fails, or the first time a compressed page is accessed in the buffer pool and the uncompressed page does not exist. The INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET tables provide ...