Re: can this be done with a check expression?

On Aug 2, 2012, at 7:10 PM, Wayne Cuddy wrote:

> I have a table with 3 columns:
>
> name text
> start_id integer
> end_id integer
>
> start_id and end_id are ranges which must not overlap but can have gaps
> between them. Is it possible to formulate a table check constraint that
> can verify that either id does not fall within an existing range at
> insert time? IE prevent overlaps during insert?
>
> Thanks,
> Wayne

So this answer will not help you for the here-and-now, but Postgres 9.2 is going to be released in the near future (though the beta is available) and contains "range types" which have check constraints on them:

http://www.postgresql.org/docs/9.2/static/rangetypes.html#RANGETYPES-CONSTRAINT

You could formulate a check constraint right now to do the equivalent, albeit it will involve a lot of conditions.

Jonathan