No, I just don't know much about this area and am looking at a
query for a customer and just did not understand. I think it is
working fine. Without first thinking about it, i saw it was something
like an 7 table and 17 way join and was surprised that the optimizer
actually was only taking 1 second even when I told it to look at all
plans. But all the joins are left outer joins, so I guess there really
is only one order and only choice is type of join.
I was trying to figure out if hints would help much, but they didn't -
and now I see why. Thanks for the answer.
/mikem
Rick Hillegas wrote:
Mike Matrigali wrote:
if my multi table query only includes a series of left outer joins,
does this force the optimizer to only choose that order of tables,
unlike a regular join where it will consider various orders?
/mikem
Hi Mike,
I haven't looked at the code but that's how it should work. The
left-join operator isn't commutative or even associative, so the join
order can't be permuted. Jeff was aware of this when he wrote the
optimizer. Have you run across a nested left join where the join order
looks suspicious?
Thanks,
-Rick
