Questions concerning check constraints

On Fri, Nov 02, 2007 at 10:04:06AM +0100, Christian Rengstl wrote:

1) Is it possible to refer to a column in a different table, ie
entering a value in mytable.x should only be allowed if mytable2.y=1 for
example? I know that it is possible to use triggers to do that, but I
think adding a simple check constraint might be simpler.

you would need to make a wrapper function for the actual checking, and
then add check (function(column) = true) or something like this.

2) Is it possible to issue custom error messages in case a constraint
is violated?

if you have function based checks - sure, "raise exception"

depesz

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