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https://dev.mysql.com/doc/refman/5.7/en/join.html
MySQL supports the following JOIN syntax for the table_references part of SELECT statements and multiple-table DELETE and UPDATE statements: table_references: escaped_table_reference [, escaped_table_reference] ... index_hint: { USE {INDEX|KEY} ...
https://dev.mysql.com/doc/refman/5.7/en/nested-join-optimization.html
The following discussion refers to the join syntax described in Section 13.2.9.2, “JOIN Clause”. This is a conservative extension if we consider each comma in a list of table_reference items as equivalent to an inner join. INNER JOIN is used ...
https://dev.mysql.com/doc/refman/5.7/en/outer-join-simplification.html
At the parser stage, queries with right outer join operations are converted to equivalent queries containing only left join operations. When the optimizer evaluates plans for outer join operations, it takes into consideration only plans where, for ... Table expressions in the FROM clause of a query are simplified in many ...
https://dev.mysql.com/doc/refman/5.7/en/nested-loop-joins.html
MySQL executes joins between tables using a nested-loop algorithm or variations on it. Nested-Loop Join Algorithm Block Nested-Loop Join Algorithm Nested-Loop Join Algorithm A simple nested-loop join (NLJ) algorithm reads rows from the first table ...For example, if 10 rows are read into a buffer and the buffer is passed to the next inner loop, each row read in the inner loop can be compared against all 10 rows in the ...
https://dev.mysql.com/doc/refman/5.7/en/bnl-bka-optimization.html
In MySQL, a Batched Key Access (BKA) Join algorithm is available that uses both index access to the joined table and a join buffer. The BKA algorithm supports inner join, outer join, and semijoin operations, including nested outer joins. Benefits ...That is, it is incremental to a row from the first operand ...
https://dev.mysql.com/doc/refman/5.7/en/outer-join-optimization.html
MySQL implements an A LEFT JOIN B join_specification as follows: Table B is set to depend on table A and all tables on which A depends. Table A is set to depend on all tables (except B) that are used in the LEFT JOIN condition. The LEFT JOIN ...If ...
https://dev.mysql.com/doc/refman/5.7/en/rewriting-subqueries.html
Prior to SQL-92, outer joins did not exist, so subqueries were the only way to do certain things. Today, MySQL Server and many other modern database systems offer a wide range of outer join types. Sometimes there are other ways to test membership ...
https://dev.mysql.com/doc/refman/5.7/en/explain-output.html
EXPLAIN Output Columns EXPLAIN Join Types EXPLAIN Extra Information EXPLAIN Output Interpretation EXPLAIN Output Columns This section describes the output columns produced by EXPLAIN. rows shows the estimated number of rows examined and rows × ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-options-variables.html
0 0/1 ndb_join_pushdown System Variable ndb_join_pushdown Scope Global, Session Dynamic Yes Type Boolean Default Value ON This variable controls whether joins on NDB tables are pushed down to the NDB kernel (data nodes). This can reduce greatly the ... This section provides information about MySQL server options, server and status variables that are specific to NDB ...
https://dev.mysql.com/doc/refman/5.7/en/group-replication-system-variables.html
The system variables that are specific to the Group Replication plugin are as follows: group_replication_allow_local_disjoint_gtids_join Command-Line Format --group-replication-allow-local-disjoint-gtids-join[={OFF|ON}] Introduced 5.7.17 Deprecated ... This section lists the system variables that are specific to the Group Replication ...