Hi,

> > > select a.* from a where
> > > not exists(select * from b where a.id = b.id)
> >
> > Yes, this should be equivalent and probably faster when there are
> many
> > duplicates on the person field.
>
> Thanks for the info. Is there any perfomance difference between the
> above query and:
>
> select a.* from a where a.id not in (select id from b)
>
> The plans look the same, but my test tables are too small to show any
> difference is speed.

Internally a IN predicate with sub-select is converted to the same as a
EXISTS thus there should be no performance difference between those two.

Regards,
Arno Brinkman
ABVisie

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