Syntax:
CHECKSUM TABLE tbl_name [, tbl_name] ... [ QUICK | EXTENDED ]

CHECKSUM TABLE reports a checksum for the contents of a table. You can
use this statement to verify that the contents are the same before and
after a backup, rollback, or other operation that is intended to put
the data back to a known state. This statement requires the SELECT
privilege for the table.

Performance Considerations

By default, the entire table is read row by row and the checksum is
calculated. For large tables, this could take a long time, thus you
would only perform this operation occasionally. This row-by-row
calculation is what you get with the EXTENDED clause, with InnoDB and
all other storage engines other than MyISAM, and with MyISAM tables not
created with the CHECKSUM=1 clause.

For MyISAM tables created with the CHECKSUM=1 clause, CHECKSUM TABLE or
CHECKSUM TABLE ... QUICK returns the "live" table checksum that can be
returned very fast. If the table does not meet all these conditions,
the QUICK method returns NULL. See [HELP CREATE TABLE] for the syntax
of the CHECKSUM clause.

For a nonexistent table, CHECKSUM TABLE returns NULL and generates a
warning.

Prior to MySQL 5.6.4, CHECKSUM TABLE returned 0 for partitioned tables
unless the EXTENDED option was used. (Bug #11933226, Bug #60681)

The checksum value depends on the table row format. If the row format
changes, the checksum also changes. For example, the storage format for
VARCHAR changed between MySQL 4.1 and 5.0, so if a 4.1 table is
upgraded to MySQL 5.0, the checksum value may change.

URL: http://dev.mysql.com/doc/refman/5.6/en/checksum-table.html

