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https://dev.mysql.com/doc/refman/5.7/en/distinct-optimization.html
DISTINCT combined with ORDER BY needs a temporary table in many cases. If you do not use columns from all tables named in a query, MySQL stops scanning any unused tables as soon as it finds the first match. Because DISTINCT may use GROUP BY, learn ...
https://dev.mysql.com/doc/refman/5.7/en/drop-server.html
Dropping a server for a table does not affect any FEDERATED tables that used this connection information when they were created. DROP SERVER [ IF EXISTS ] server_name Drops the server definition for the server named server_name. DROP SERVER is not ...
https://dev.mysql.com/doc/refman/5.7/en/drop-trigger.html
DROP TRIGGER requires the TRIGGER privilege for the table associated with the trigger. Triggers for a table are also dropped if you drop the table. DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name This statement drops a trigger. If the schema is ...
https://dev.mysql.com/doc/refman/5.7/en/execution-plan-information.html
Depending on the details of your tables, columns, indexes, and the conditions in your WHERE clause, the MySQL optimizer considers many techniques to efficiently perform the lookups involved in an SQL query. A query on a huge table can be performed ...The set of operations that the optimizer chooses to perform the most efficient query is called the “query execution plan”, also known as the EXPLAIN ...
https://dev.mysql.com/doc/refman/5.7/en/expressions.html
The following table shows the expected form of the expr argument for each unit value. This section lists the grammar rules that expressions must follow in MySQL and provides additional information about the types of terms that may appear in ...
https://dev.mysql.com/doc/refman/5.7/en/federated-storage-engine.html
Querying a local FEDERATED table automatically pulls the data from the remote (federated) tables. The FEDERATED storage engine lets you access data from a remote MySQL database without using replication or cluster technology. To include the ...
https://dev.mysql.com/doc/refman/5.7/en/group-replication-secure-socket-layer-support-ssl.html
Once the donor is selected, the server joining the group establishes an asynchronous replication connection. new_member> CHANGE MASTER TO MASTER_USER="rec_ssl_user" FOR CHANNEL "group_replication_recovery"; new_member> START GROUP_REPLICATION; ...
https://dev.mysql.com/doc/refman/5.7/en/index-preloading.html
Preloading enables you to put the table index blocks into a key cache buffer in the most efficient way: by reading the index blocks from disk sequentially. If there are enough blocks in a key cache to hold blocks of an entire index, or at least the ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-deadlocks.html
A deadlock can occur when transactions lock rows in multiple tables (through statements such as UPDATE or SELECT ... A deadlock is a situation in which multiple transactions are unable to proceed because each transaction holds a lock that is needed ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-memcached.html
The InnoDB memcached plugin (daemon_memcached) provides an integrated memcached daemon that automatically stores and retrieves data from InnoDB tables, turning the MySQL server into a fast “key-value store”. You can also access the same InnoDB ...Instead of formulating queries in SQL, you can use simple get, set, and incr operations that avoid the performance overhead associated with SQL parsing and constructing a query optimization ...