Re: [SQL] Update problem I cannot work out
От | M Simms |
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Тема | Re: [SQL] Update problem I cannot work out |
Дата | |
Msg-id | 199905021224.NAA15135@argh.demon.co.uk обсуждение исходный текст |
Ответ на | RE: [SQL] Update problem I cannot work out (Michael J Davis <michael.j.davis@tvguide.com>) |
Ответы |
Re: [SQL] Update problem I cannot work out
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Список | pgsql-sql |
> > Try something like: > > Create function new_function(value_data_type) > 'Select sum(t1.var1) from t1 where t1.var2 = $1' LANGUAGE > 'sql'; > > update t2 set var1=t2.var1+new_function(t2.var2); > *snip* Hi, thanks for replying. My reply to this is the question, that as each function contains a select, is this technically a single pass. I get the feeling there will be tremendous overhead on this theory with a large dataset, in comparison to a single query that does the update. Can anyone comment on how much slower this could be (although obviously if there is no way to do it in a single query then there is no choice)? Thanks M Simms
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