On Mon, 2003-06-09 at 08:00, James Taylor wrote: > I've got three tables, I'll shorten the columns down just so you get the > idea: > > lists > ----------- > id|order_id > > list_results > ------------ > id|lid|total > > orders > ------------ > id|max > > All of the columns are int's. What I'm trying to do is something like: > > select (o.max-coalesce(sum(lr.total),0)) from orders o,list_results lr > where lr.l_id in (select > l.id from lists l, orders o where l.order_id=X and o.id=l.order_id) > group by o.max > > This would, in theory, return a number which should be > o.total-sum(lr.total) > > The problem is, there may not be any data in list_results OR lists > regarding the order ID. If data from list_results.total exists, and is > referencing lists.id, which in turn is referencing orders.id through > lists.order_id, return o.max-lr.total. If data from list_results or > lists DOESN'T exist, I would just want to go ahead and return > orders.max. I was hoping the coalesce would be able to do this, but it > doesn't. The subquery is in there because frankly I'm not sure how to > do multiple left joins, which I think would have to exist. The easy way > out for me here I think would be to make list_results.order_id and leave > lists out of it, but then I'd have redundant data in two tables. Any > suggestions on this one?
Multiple left outer joins? FROM <tab> LEFT OUTER JOIN <tab2> USING (<column>) LEFT OUTER JOIN <tab3> USING (<column>) WHERE ... In your case, SELECT (o.max - coalesce(sum(lr.total), 0)) FROM orders LEFT OUTER JOIN lists ON (orders.id = lists.order_id) LEFT OUTER JOIN list_results ON (lists.id = list_results.l_id) GROUP BY o.max But I'm not sure if that accomplishes what you're looking for or not. -- Rod Taylor <[EMAIL PROTECTED]> PGP Key: http://www.rbt.ca/rbtpub.asc
signature.asc
Description: This is a digitally signed message part
