"Demel, Jeff" <Jeff.Demel@xxxxxxxxxxxxxxxxx> writes: > Here's what I came up with: > SELECT customers.id, customers.firstname, > customers.lastname, customers.phone number, > (SELECT ar.billdate FROM ar > WHERE customers.customerid = ar.customerid > ORDER BY ar.billdate LIMIT 1) > AS lastarbilldate > FROM customers > WHERE customers.status = 'new'; Are you expecting a whole lot of answer rows from this query, or just a few? If just a few, this way is fine, but if a lot you probably want to try to recast it as a join. As is, it's pretty much like a nestloop join of the two tables, which is good for a few result rows and not so good for a lot. The thing you need to make it fast as a subselect is an index on (customerid, billdate) in that order. Oh, you also need PG 8.1 or later, but I see you have that. Personally I'd just write (SELECT max(billdate) FROM ar WHERE customers.customerid = ar.customerid) rather than trying to get cute with ORDER BY/LIMIT --- the planner versions that are able to handle this case decently will deal with either one about as well. regards, tom lane
