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BOOK: Beginning Database Design Solutions ISBN: 978-0-470-38549-4
This is the forum to discuss the Wrox book Beginning Database Design Solutions by Rod Stephens; ISBN: 9780470385494
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Old May 2nd, 2012, 01:28 PM
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Default CHECK constraint

I have a problem with CONSTRAINTs
This is what I am using:

mysql> SHOW VARIABLES LIKE "%version%";
| Variable_name | Value |
| innodb_version | 1.1.8 |
| protocol_version | 10 |
| slave_type_conversions | |
| version | 5.5.16 |
| version_comment | MySQL Community Server (GPL) |
| version_compile_machine | x86 |
| version_compile_os | Win32 |

I tried to add a CHECK constraint for the gender. I tried both these and without success. I saw a lot of people report it as a bug, but not sure if it's a but or I do something wrong.

CHECK(gender IN ('M', 'F'));
CHECK (gender LIKE '[MF]');
I tried

as well as

CONSTRAINT ck_gender CHECK (gender in ( 'M', 'F' ) )
when define the table.

Is my syntax wrong? Thank you for your time.

Last edited by masterlayouts; May 2nd, 2012 at 01:31 PM..
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Old May 2nd, 2012, 04:10 PM
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Sorry but both of those look valid to me. But I've seen some posts that say MySQL doesn't support CHECK constraints. See this thread:


Be sure to read the replies. They say you may be able to use a trigger to perform the job of the CHECK constraint.

In this case you could also build a lookup table and use it as a foreign key to validate the field. That seems like serious overkill but it should work.

Rod Stephens, Microsoft MVP

Essential Algorithms: A Practical Approach to Computer Algorithms

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