Re: Subselects in CHECK clause ...

[James Robinson <jlrobins(at)socialserve(dot)com>]

Gotcha. This is indeed to ensure a specialized ref integrity bit,  
against a column which "ought not ever change". Once some more old  
code goes away, then can fully normalize this area, making this check  
subselect bit go away, replaced by a regular FK.

Hmm -- probably could even now make it a FK against a column which is  
not the pri key of the foreign table, and it'd work better and would  
ensure consistence against changes on the foreign table side, eh?

Thanks!

On Nov 29, 2006, at 12:53 PM, Stephan Szabo wrote:

> To completely get the constraint, you have to also apply  
> constraints on
> the tables referenced in the function that prevent modifications on  
> those
> tables from causing the constraint to be violated. For example, if you
> were to do an exists test on another table for a row that matches  
> up with
> this row in some fashion (for a specialized referential integrity
> constraint) modifications on that other table could also cause the
> constraint to be violated, but that isn't caught by the CHECK
> function(...) case and you'll probably need triggers or other  
> constraints
> on that table.

----
James Robinson
Socialserve.com