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

CHECKSUM TABLE reports a checksum for the contents of a table. During
the checksum operation, the table is locked with a read lock for InnoDB
and MyISAM. 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.

This statement is not supported for views. If you run CHECKSUM TABLE
against a view, the Checksum value is always NULL, and a warning is
returned.

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.

The checksum value depends on the table row format. If the row format
changes, the checksum also changes. For example, the storage format for
temporal types such as TIME, DATETIME, and TIMESTAMP changed in MySQL
5.6 prior to MySQL 5.6.5, so if a 5.5 table is upgraded to MySQL 5.6,
the checksum value may change.

URL: http://dev.mysql.com/doc/refman/5.7/en/checksum-table.html

