> > I'm trying to do a multi-column update, adding values from another
> table. Something like:
> >
> > UPDATE t1 SET a += (SELECT a FROM t2 WHERE t1.id = t2.id),
> > b += (SELECT b FROM t2 WHERE t1.id =
> > t2.id);
>
> This particular query need not be very inefficient if the pages needed
> to do the second sub-query are left in the cache from the first sub-
> query...
No. That's true. But this is just a simple example. It's possible that the
sub-select is much more complicated.
By the way, the syntax diagram doesn't allow "+=" so how would the above be
coded in reality?
This way?
UPDATE t1 SET a = (SELECT t1.a + t2.a FROM t2 WHERE t1.id = t2.id),
b = (SELECT t1.b + t2.b FROM t2 WHERE t1.id = t2.id)
Or...
UPDATE t1 SET a = t1.a + (SELECT t2.a FROM t2 WHERE t1.id = t2.id),
b = t1.b + (SELECT t2.b FROM t2 WHERE t1.id = t2.id)
Marc
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