Re: How to find entries missing in 2nd table?
| От | Aaron Bono |
|---|---|
| Тема | Re: How to find entries missing in 2nd table? |
| Дата | |
| Msg-id | bf05e51c0607130925u12635434v98d877a7f1eb449a@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: How to find entries missing in 2nd table? (Richard Broersma Jr <rabroersma@yahoo.com>) |
| Ответы |
Re: How to find entries missing in 2nd table?
|
| Список | pgsql-sql |
On 7/13/06, Richard Broersma Jr <rabroersma@yahoo.com> wrote:
So in that case this would be better:
SELECT controller_id FROM control
WHERE controller_id NOT IN
(SELECT controller_id FROM datapack);
or
SELECT controller_id FROM control
WHERE controller_id NOT IN
(SELECT controller_id FROM datapack GROUP BY controller_id);
Guess you need to do some explain plans to see which would be best.
Good luck!
==================================================================
Aaron Bono
Aranya Software Technologies, Inc.
http://www.aranya.com
==================================================================
> > SELECT controller_id FROM control
> > WHERE controller_id NOT IN
> > (SELECT DISTINCT controller_id FROM datapack);
> The DISTINCT is not necessary. I have heard with Oracle that DISTINCT is a
> huge performance problem. Is that true on PostgreSQL also?
From my experience, it does not preform as well as the standard group by clause. I noticed a ~20%
increase in query run times.
So in that case this would be better:
SELECT controller_id FROM control
WHERE controller_id NOT IN
(SELECT controller_id FROM datapack);
or
SELECT controller_id FROM control
WHERE controller_id NOT IN
(SELECT controller_id FROM datapack GROUP BY controller_id);
Guess you need to do some explain plans to see which would be best.
Good luck!
==================================================================
Aaron Bono
Aranya Software Technologies, Inc.
http://www.aranya.com
==================================================================
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