Re: [SQL] subquery, except and view

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От Tom Lane
Тема Re: [SQL] subquery, except and view
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Msg-id 9193.944767220@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: [SQL] subquery, except and view  (wieck@debis.com (Jan Wieck))
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wieck@debis.com (Jan Wieck) writes:
>> test :>select client.num_clt, client.name from client, commamount where
>> test :>(client.num_clt = commamount.num_clt) and
>> test :>(3 > howmuch);
>> 
>> This seems to do the job perfectly. Notice the value preceeding the
>> column name in the comparison. Seems nescesary ...

>     Is  definitely  necessary,  because 'howmuch' is an aggregate
>     column  and  the  rewriter  can  only  put  that   into   the
>     qualification  if  the  aggreate  is on the right side of the
>     comparision.

BTW, this restriction is no longer true in current sources, since
single-result sub-SELECTs can now appear anywhere in an expression...
        regards, tom lane


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