Re: Views with joins

==========James_F_Davis_at_NSLC.FMSO.NAVY.MIL, 5/04/95========== Are queries against views with built-in joins slowed down by the join if the user selects only columns from one of the joined tables?

I would say so. Condsider this:

create view ab as select * from a,b
where a.a=b.b
and a.c=x
and b.d=y;

select a from ab;

The join has to be performed to determine which rows drop out of the join. If the optimiser is very clever - and Oracle's usually isn't all that clever - it may be able
to spot instances where the join is not required. This will probably not occur consistently if at all. If there is only one rule for all joins within views, the rule would
be that the join must be performed. Received on Fri Jun 30 1995 - 00:00:00 CEST