--- Tom Lane <[EMAIL PROTECTED]> wrote:
> Ludwig Lim <[EMAIL PROTECTED]> writes:
> > 1) Is the ON clause of an OUTER JOIN always
> > evaluated first before the WHERE clause?
>
> No; the planner will do whatever it thinks is the
> most efficient way
> (assuming it can prove that the reordering it wants
> to do won't change
> the query result).
If re-ordering does change the result, is the ON
clause evaluated first and the WHERE filters out the
result of the OUTER JOIN?
> > Is there a way to rewrite the query as a view
> such
> > that one can do:
>
> I'm really not clear on what you want here. Better
> example please?
>
Sorry for not making it that clear.
Is there way of rewritting :
SELECT a.status,
employee_id
FROM permission a LEFT JOIN
( SELECT * FROM employee WHERE employee_id
=5) as b ON (a.status = b.status)
WHERE status='test'
into a query that has no subselect in the FROM clause.
I mean can the query above be rewritten into
something like:
SELECT a.status,
b.employee_id
FROM permission a LEFT JOIN employee b ON
(a.status = b.status)
WHERE a.status = 'test' and
b.employee_id = 5;
Thank you very much,
ludwig
__________________________________
Do you Yahoo!?
SBC Yahoo! DSL - Now only $29.95 per month!
http://sbc.yahoo.com
---------------------------(end of broadcast)---------------------------
TIP 5: Have you checked our extensive FAQ?
http://www.postgresql.org/docs/faqs/FAQ.html
