On Sun, 2006-07-30 at 20:20 -0400, Robert Treat wrote: > On Thursday 27 July 2006 09:28, Bruce Momjian wrote: > > Tom Lane wrote: > > > Bruce Momjian <[EMAIL PROTECTED]> writes: > > > > Tom Lane wrote: > > > >> UPDATE mytab SET (foo, bar, baz) = > > > >> (SELECT alpha, beta, gamma FROM othertab WHERE key = mytab.key); > > > > > > > > That UPDATE example is interesting because I remember when using > > > > Informix that I had to do a separate SELECT statement for each UPDATE > > > > column I wanted to update. I didn't realize that you could group > > > > columns and assign them from a single select --- clearly that is a > > > > powerful syntax we should support some day. > > > > > > No question. The decision at hand is whether we want to look like > > > we support it, when we don't yet. I'd vote not, because I think the > > > main use-case for the row-on-the-left syntax is exactly this, and > > > so I fear people will just get frustrated if they see it in the > > > syntax synopsis and try to use it. > > > > I'm not a big fan of implementing partial solutions (remember "left-joins are > not implemented messages" :-) way back when) , however in my experience with > this form of the update command, the primary usage is not to use a subselect > to derive the values, but to make it easier to generate sql, using a single
I disagree. UPDATE mytab SET (foo, bar, baz) =(SELECT ...) is the specifications way of doing an update with a join. That is its primary purpose. UPDATE ... FROM is a PostgreSQL alternative to the above. -- ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend