Re: Providing an alternative result when there is no result

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От Merlin Moncure
Тема Re: Providing an alternative result when there is no result
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Msg-id b42b73150905200446j5b0a55d6n7bd4ed3b5e93f492@mail.gmail.com
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Ответ на Re: Providing an alternative result when there is no result  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Tue, May 19, 2009 at 7:00 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Merlin Moncure <mmoncure@gmail.com> writes:
>> On Mon, May 18, 2009 at 3:13 PM, Joshua Berry <yoberi@gmail.com> wrote:
>>> Is there an easy and efficient way to return a boolean false for a query
>>> that returns no result, and true for one that does return a result?
>
>> Probably the best general approach is to:
>
>> select count(*) = 1 from
>> (
>>   <query> limit 1
>> )q;
>
> Seems like EXISTS() is much more straightforward ...

yes...I didn't notice david's response upthread.  that is indeed very elegant.

merlin

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