Help with constraints

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#180

From: arabub
Date: Thu, 01 Nov 2001 21:15

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How can I create a table so that certain constraints are already built
in, and automatically enforced on every insert?

Example: A table has a column "foo" and a column "bar". Either or both
can be NULL. Only one of them can be not NULL. I.e. if foo is not NULL
then bar must be NULL, and vice-versa. Whenever I try to insert a row
with both foo and bar not NULL, then I want an error.

Is there a way to write query on a table that will tell me whether
such constrainst exist, and what they are?

Thanks!

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Subject: Help with constraints
Date: 1 Nov 2001 13:15:50 -0800
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