Subject Re: [firebird-support] Re: check constraint to enforce uniqueness
Author Helen Borrie
At 06:33 AM 4/01/2005 +0000, you wrote:

>Thanks, Helen, Adam, but as in my check constraint, SERIALNO can be
>null, so I can't define a unique constraint on the 4 columns since
>SERIALNO does not always have a value. In cases when SERIALNO does
>have a value, I'd like to enforce the uniqueness on the 4 columns.

A unique constraint can contain nulls.

>Any other way to do this if it can't be done thru a check constraint?

Nothing that I would recommend.