Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> c.d.o.server -> Re: What does "push a join predicate down" mean ?
"Nejjari" <nejjari_at_yahoo.fr> wrote in message
news:28e0d9.0407130802.464ef36f_at_posting.google.com...
> Hi,
>
> For example: You have a simple Select col_1, col_2 from some_table
> defined as a view named base_view. If you issue the following query
> Select count(*) from base_view where col_1 = A and col_2 = B and there
> is an index on the 2 columns, the Optimizer will merge the use of the
> two columns into the view and the EXPLAIN_PLAN will reflect this along
> with the use of the Indexes on the individual tables.
But col_1 = A looks like a single table predicate to me. Perhaps the query should be like this
alter session set "_push_join_union_view2"=true;
alter session set "_push_join_union_view"=true;
select 1 from emp, (
select deptno from dept where dname= '1'
union all
select deptno from dept where dname= '2'
) v where v.deptno = emp.deptno
? However, no matter what I tried, join predicate is not pushed down. Received on Tue Jul 13 2004 - 12:52:13 CDT