The MySQL Reference Manual says:
The CHECK clause is parsed but ignored by all storage engines.
No mistake. I've read that over 10 times.
So what's the whole point of writing check constraints then?
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Emre Yazici
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Yony
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3The real question is: why does MySQL still not support them... – Jul 09 '11 at 18:03
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possible duplicate of [check constraint in mysql not working](http://stackoverflow.com/questions/2115497/check-constraint-in-mysql-not-working) and others – gbn Jul 09 '11 at 19:35
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It's there because of interoperability concerns. You can for example import an SQL script that is generated by other RDBMSs that support CHECK constraint (say Oracle).
Emre Yazici
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There is no point. I think they prepared the database to accept check constraints by adding support for them in the SQL parser but none of the engines still support them.
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It's been a bug report for over 7 years.
http://bugs.mysql.com/bug.php?id=3464
Personal opinion: another reason not to use MySQL, like NATURAL JOIN (and again) and random aggregates
