CHECKSUM TABLE tbl_name [, tbl_name] ... [ QUICK | EXTENDED ]
CHECKSUM TABLE reports a table checksum. This is very
useful if you want to know if two tables are the same (for example on a master
QUICK, the live table checksum is reported if it is
NULL otherwise. This is very fast. A live
checksum is enabled by specifying the
option when you create the table; currently, this is supported
only for Aria and MyISAM tables.
EXTENDED, the entire table is read row by row and the
checksum is calculated. This can be very slow for large tables.
specified, MariaDB returns a live checksum if the table storage engine supports
it and scans the table otherwise.
CHECKSUM TABLE requires the SELECT privilege for the table.
For a nonexistent table,
CHECKSUM TABLE returns
NULL and generates a warning.
The table row format affects the checksum value. If the row format changes, the checksum will change. This means that when a table created with a MariaDB/MySQL version is upgraded to another version, the checksum value will probably change.
Two identical tables should always match to the same checksum value; however, also for non-identical tables there is a very slight chance that they will return the same value as the hashing algorithm is not completely collision-free.
Differences between MariaDB and MySQL
CHECKSUM TABLE may give a different result as MariaDB doesn't
NULLs in the columns as MySQL 5.1 does (Later MySQL
versions should calculate checksums the same way as MariaDB). You can get the
'old style' checksum in MariaDB by starting mysqld with the
--old option. Note however that that the MyISAM and Aria
storage engines in MariaDB are using the new checksum internally, so if you are
CHECKSUM command will be
slower as it needs to calculate the checksum row by row.