Re: Setting a default value for a select statement without results

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От JORGE MALDONADO
Тема Re: Setting a default value for a select statement without results
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Msg-id CAAY=A79wHndbO4FGOU6O4-zmSJTDiDK8syiq1cpNr_=z4L7uMA@mail.gmail.com
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Ответ на Re: Setting a default value for a select statement without results  (Jasen Betts <jasen@xnet.co.nz>)
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This solution gave me the result I need, but it seems the process takes longer when COALESCE is added.

What do you mean with the comment of "and you are happy with its performance" ?
Does it have to do with performance?

Regards,
Jorge Maldonado


On Tue, Feb 5, 2013 at 10:07 PM, Jasen Betts <jasen@xnet.co.nz> wrote:
On 2013-02-06, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:
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> I have an UPDATE query with the following general structure:
>
> UPDATE table1 SET (SELECT field FROM table2 WHERE conditions ORDER BY
> order_field LIMIT 1)

assuming you mean this, and you are happy with its performance.

 UPDATE table1 SET field1 = (SELECT field FROM table2 WHERE conditions ORDER BY
 order_field LIMIT 1)


> Is it possible to assign a default value in case no results are returned by
> the SELECT statement?

use coalesce.

 UPDATE table1 SET field1 = coalesce( (SELECT field FROM table2 WHERE conditions ORDER BY
 order_field LIMIT 1) , default_value )




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