Re: - Slow Query

On Wed, Jul 1, 2009 at 11:52 AM, Tom Lane<tgl@sss.pgh.pa.us> wrote:
> Scott Marlowe <scott.marlowe@gmail.com> writes:
>> Sometimes putting a where clause portion into the on clause helps.
>> like:
>> select * from a left join b on (a.id=b.id) where a.somefield=2
>> might run faster with
>> select * from a left join b on (a.id=bid. and a.somefield=2);
>> but it's hard to say.
>
> Uh, those are not the same query ... they will give different results
> for rows with a.somefield different from 2.

How so?  Neither should return any rows with a.somefield <> 2.  Or are
you talking where a.somefield is null?