Re: SQL Question

Thanks I eventually came to the same conclusion as your first
suggested answer, but don't really understand the second one.  Can you
explain why the second one works?  It is faster.  I looked at the
query plans and the second does seem like it would be much faster.

First:
Sort  (cost=99164.54..99165.04 rows=200 width=2)
  Sort Key: personid
  ->  HashAggregate  (cost=82905.40..99156.90 rows=200 width=2)
        ->  Seq Scan on test a  (cost=0.00..82885.00 rows=2040 width=2)
              SubPlan
                ->  Aggregate  (cost=40.61..40.62 rows=1 width=0)
                      ->  Seq Scan on test b  (cost=0.00..40.60 rows=1 width=0)
                            Filter: ((typeid = 3) AND (personid = $0))
        SubPlan
          ->  Aggregate  (cost=40.61..40.62 rows=1 width=0)
                ->  Seq Scan on test b  (cost=0.00..40.60 rows=1 width=0)
                      Filter: ((typeid = 3) AND (personid = $0))

Second:
Sort  (cost=158.59..159.09 rows=200 width=4)
  Sort Key: ev.personid
  ->  HashAggregate  (cost=142.45..150.95 rows=200 width=4)
        ->  Hash Left Join  (cost=45.65..106.75 rows=2040 width=4)
              Hash Cond: (("outer".personid = "inner".personid) AND
("outer".rowid = "inner".rowid))
              ->  Seq Scan on test ev  (cost=0.00..30.40 rows=2040 width=4)
              ->  Hash  (cost=35.50..35.50 rows=2030 width=4)
                    ->  Seq Scan on test ev2  (cost=0.00..35.50
rows=2030 width=4)
                          Filter: (typeid <> 3)

Ketema J. Harris
www.ketema.net
ketema@ketema.net