Re: Should Aggregate Functions always return one row?

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От Tom Lane
Тема Re: Should Aggregate Functions always return one row?
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Msg-id 16437.1074998751@sss.pgh.pa.us
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Ответ на Should Aggregate Functions always return one row?  (wilhelm.pakulla@gmx.de)
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wilhelm.pakulla@gmx.de writes:
> So, if I use the max() aggregate, I receive one row with the value NULL. Is
> that correct?

Yup, that's what the SQL spec says to do, and it seems reasonable to me.

IIRC, the spec also says that SUM() over no rows returns NULL, which is
less reasonable --- I'd have defined it as returning zero, myself.
But when in doubt we follow the spec.

            regards, tom lane

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