Re: [HACKERS] subselects

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От darrenk@insightdist.com (Darren King)
Тема Re: [HACKERS] subselects
Дата
Msg-id 9801211413.AA36452@ceodev
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Ответы Re: [HACKERS] subselects  (Bruce Momjian <maillist@candle.pha.pa.us>)
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> We are only going to have subselects in the WHERE clause, not in the
> target list, right?
>
> The standard says we can have them either place, but I didn't think we
> were implementing the target list subselects.
>
> Is that correct?

What about the HAVING clause?  Currently not in, but someone here wants
to take a stab at it.

Doesn't seem that tough...loops over the tuples returned from the group
by node and checks the expression such as "x > 5" or "x = (subselect)".

The cost analysis in the optimizer could be tricky come to think of it.
If a subselect has a HAVING, would have to have a formula to determine
the selectiveness.  Hmmm...

darrenk

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