Re: Insert performance (OT?)
От
Manfred Koizar
Тема
Re: Insert performance (OT?)
Дата
Msg-id
cs67g11p5k1pfkf6kcuvpnjubmmeutcni2@4ax.com
Ответ на
Re: Insert performance (OT?) (Richard Huxton)
Список
Дерево обсуждения
Insert performance (OT?) Yves Vindevogel <yves.vindevogel@implements.be>
Re: Insert performance (OT?) Yves Vindevogel <yves.vindevogel@implements.be>
Re: Insert performance (OT?) Richard Huxton <dev@archonet.com>
On Tue, 19 Jul 2005 11:51:51 +0100, Richard Huxton wrote: >You could get away with one query if you converted them to left-joins: >INSERT INTO ... >SELECT * FROM upload LEFT JOIN ... WHERE f3 IS NULL >UNION >SELECT * FROM upload LEFT JOIN ... WHERE f4 IS NULL For the archives: This won't work. Each of the two SELECTs eliminates rows violating one of the two constraints but includes rows violating the other constraint. After the UNION you are back to violating both constraints :-( Servus Manfred
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