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EXPLAIN returns information about index usage, as well as being a synonym for DESCRIBE.
Shows an execution plan for a running query.
Old implementation, now ANALYZE statement
The EXPLAIN Analyzer is no longer active. The EXPLAIN Analyzer was an online tool for analyzing and optionally sharing the output of both EXPLAIN and EXPLAIN EXTENDED. Using t...
Articles on the ANALYZE and EXPLAIN statements
Variant of EXPLAIN that produces output in JSON form
The online EXPLAIN Analyzer tool has an open API to allow client applications to send it EXPLAINs. Sending EXPLAINs to the EXPLAIN Analyzer To send an EXPLAIN to the EXPLAIN A...
Listing of things to improve in MySQL's implementation of EXPLAIN FORMAT=JSON
EXPLAIN output in the slow query log.
Error 1791: Unknown EXPLAIN format name: '%s'
Differences between MariaDB's and MySQL's EXPLAIN JSON output.
Error 1345: EXPLAIN/SHOW can not be issued; lacking privileges for underlying table
Error 3012: EXPLAIN FOR CONNECTION command is supported only for SELECT/UPDATE/INSERT/DELETE/REPLACE
Optimizer Feature Comparison Matrix
Overview of Query Optimizer in Recent Versions of MariaDB.
Table Elimination User Interface and EXPLAIN.
index_merge is a method used by the optimizer to retrieve rows from a single table using several index scans. The results of the scans are then merged. When using EXPLAIN, if ...
Notes about Optimizer Development mysql-test InnoDB Estimates are unstable This is caused by background statistics update. It may cause the numbers in EXPLAIN output to be of...
MariaDB 5.3 introduced the derived table merge optimization.
Handles equality comparisons like utf8mb3_key_column=utf8mb4_expression.
Invokes the optimizer, executes the statement, and then produces EXPLAIN output.
DuplicateWeedout is an execution strategy for Semi-join subqueries.
Transfers a result set from a prepared statement.
Semi-join Materialization is a subquery materialization used for Semi-join subqueries.
This is SergeyP's list of patches in MySQL 5.6 that he has found interesting. It is not a full list of interesting features or anything like that WL#6071: Inline tmp tables in...