On Mon, Jul 24, 2006 at 12:51:48PM -0500, Bruno Wolff III wrote: > On Mon, Jul 24, 2006 at 09:59:07 +0100, > Richard Jones <[EMAIL PROTECTED]> wrote: > > On Sun, Jul 23, 2006 at 01:32:37PM -0500, Bruno Wolff III wrote: > > > On Sat, Jul 22, 2006 at 14:32:57 +0100, > > > Richard Jones <[EMAIL PROTECTED]> wrote: > > > > > > > > Now I want to add a column to page_contents, say called link_name, > > > > which is going to reference the pages.url column for the particular > > > > host that this page belongs to. > > > > > > What are you trying to accomplish by this? > > > > Data integrity. > > This doesn't make sense in isolation. If that is all you are trying to do, > then you don't need to do anything to the database design as the information > is already there. The application just needs to do a join when querying the > data.
I'm not sure what this means. By "data integrity" I just meant that I don't want applications to create page_contents.link_name fields which could point to non-existent URLs. (A URL consists of a particular hostid and url, since you're not allowed to have one host pointing to pages on another, and this is where the requirement for a foreign key which spans two tables comes from). Perhaps I meant "data consistency"? Anyway without some sort of check, be it a reference or a trigger -- assuming a trigger is possible -- then an application might create such a bad link. Rich. -- Richard Jones, CTO Merjis Ltd. Merjis - web marketing and technology - http://merjis.com Team Notepad - intranets and extranets for business - http://team-notepad.com ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
