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EXPLAIN [explain_type] SELECT select_options

explain_type:
    EXTENDED
  | PARTITIONS

Or:

EXPLAIN tbl_name

The EXPLAIN statement can be used either as a way to obtain information about how MySQL executes a statement, or as a synonym for DESCRIBE:

When you precede a SELECT statement with the keyword EXPLAIN, MySQL displays information from the optimizer about the query execution plan. That is, MySQL explains how it would process the statement, including information about how tables are joined and in which order. EXPLAIN EXTENDED can be used to obtain additional information.

For information about using EXPLAIN and EXPLAIN EXTENDED to obtain query execution plan information, see Section 8.8.1, “Optimizing Queries with EXPLAIN”.
EXPLAIN PARTITIONS is useful only when examining queries involving partitioned tables. For details, see Section 18.3.4, “Obtaining Information About Partitions”.
EXPLAIN tbl_name is synonymous with DESCRIBE tbl_name or SHOW COLUMNS FROM tbl_name. For information about DESCRIBE and SHOW COLUMNS, see Section 13.8.1, “DESCRIBE Syntax”, and Section 13.7.5.6, “SHOW COLUMNS Syntax”.

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