A note on Baron's command line tip for comparing result sets

April 16, 2009

A while ago Baron Schwartz published a MySQL command-line tip: compare result sets.

A "SELECT * FROM world", for example, can be checksummed, compared with another checksum made on a replica, or otherwise another table which is supposed to contains the exact same data.

I just wanted to note that if you're dealing with a MyISAM table, a simple "SELECT * FROM" will not necessarily be too useful, since MyISAM can store rows in any particular order: two different settings of concurrent_insert, or perhaps an OPTIMIZEd table, can make for different ordering, hence different checksums.

Use of "ORDER BY ..." is required if you want to have a consistent checksum. With MyISAM, you don't usually want to count on natural row ordering, at any case.

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