Re: Recursive closure
From: Jan Hidders <hidders_at_REMOVE.THIS.win.tue.nl>
Date: 5 Jul 2001 11:22:49 GMT
Message-ID: <9i1im9$2ij$1_at_news.tue.nl>
Date: 5 Jul 2001 11:22:49 GMT
Message-ID: <9i1im9$2ij$1_at_news.tue.nl>
Tim Galle wrote:
> I have a table with a recursive relation. Something like:
> tblName(Number (PK), Name, SuperNumber (FK) )
>
> I would like to create a query who gives all the names at all the levels.
> (number differs from record to record) You can't do that in SQL2,
> but I heared it was possible in SQL3.
>
> How do you write this in relational algebra?
You don't. The transitive closure is not expressible in the standard relational algebra.
-- Jan HiddersReceived on Thu Jul 05 2001 - 13:22:49 CEST