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(mysql.info)ANALYZE TABLE

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`ANALYZE TABLE' Syntax
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     ANALYZE TABLE tbl_name[,tbl_name...]

Analyze and store the key distribution for the table.  During the
analyze the table is locked with a read lock.  This works on `MyISAM'
and `BDB' tables.

This is equivalent to running `myisamchk -a' on the table.

MySQL uses the stored key distribution to decide in which order tables
should be joined when one does a join on something else than a constant.

The command returns a table with the following columns:

*Column*                  *Value*
Table                     Table name
Op                        Always "analyze"
Msg_type                  One of `status', `error', `info' or `warning'.
Msg_text                  The message.

You can check the stored key distribution with the `SHOW INDEX' command.
Note: SHOW DATABASE INFO.

If the table hasn't changed since the last `ANALYZE TABLE' command, the
table will not be analyzed again.