Re: HAVING ...

"Marc G. Fournier" <scrappy@postgresql.org> writes:
> Is there a reason (other then it hasn't been implemented yet?) that the 
> following couldn't work?

>    SELECT id,count(id) AS cnt
>      FROM table
>     WHERE id IN ( 1,2,3,4,5)
> GROUP BY id
>    HAVING cnt = 2;

It's contrary to the SQL spec, for one thing ...

>    SELECT id,count(id) AS cnt
>      FROM table
>     WHERE id IN ( 1,2,3,4,5)
> GROUP BY id
>    HAVING count(id) = 2;

> The second one would have to 're-run' the COUNT against the table, would 
> it not?

No, it doesn't.  We've optimized out duplicate aggregate calls for
awhile now.
        regards, tom lane