On Thu, Mar 09, 2006 at 12:56:21 -0500, Chris Kratz <chris.kratz@xxxxxxxxxxxxxx> wrote: > Hello All, > > Is there any way in postgres to have an aggregate that uses input from two > columns without using composite types? The example we are working on is a > first or last aggregate which requires a data value and a date column. The > result would be to find the latest date within the group and return the > associated data value. Since there may be multiple date columns each with > dependent columns, we can't use a sort by date and a simpler first or last > aggregate. It sounds like you could use the (postgres specific) DISTINCT ON construct to do what you are looking for. Something like: SELECT DISTINCT ON (groupcol) datacol ORDER BY groupcol DESC, datecol DESC; If there are multiple versions of this being done at the same time, you can do them separately and then join then on the group key (groupcol in the example).
