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 | | From: | KÖPFERL_Robert | | Subject: | Inserting or Deleting conditionally | | Date: | Mon, 17 Jan 2005 16:25:59 +0100 |
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 | Hi,
coming from imperative programming paradigma, I'm currently trying to
express something like that in _SQL_:
It should be atomic and like an API for a user. I'm therefore writing
functions:
CRETE FUNC...
c := SELECT x,y,z FROM table_a WHERE...
IF COUNT(c)=1 then
INSERT / DELETE ... WHERE x = c.x
ENDIF
LANGUAGE SQL;
How is this correctly formulated? Or is there no other way than PL/xxx?
Thanks
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| | From: | Richard Huxton | | Subject: | Re: Inserting or Deleting conditionally | | Date: | Mon, 17 Jan 2005 16:02:46 +0000 |
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| KÖPFERL Robert wrote:
> Hi,
>
> coming from imperative programming paradigma, I'm currently trying to
> express something like that in _SQL_:
SQL is not an imperative language - each SQL statement is an expression
to be evaluated.
> It should be atomic and like an API for a user. I'm therefore writing
> functions:
>
> CRETE FUNC...
>
> c := SELECT x,y,z FROM table_a WHERE...
> IF COUNT(c)=1 then
> INSERT / DELETE ... WHERE x = c.x
> ENDIF
Even if this was valid syntax, you've just made your query N times more
expensive. Try something like:
INSERT ... WHERE x IN (SELECT x FROM table_a WHERE ...)
or similar.
> How is this correctly formulated? Or is there no other way than PL/xxx?
Sounds like you want a middle-ware layer to provide an API for your
applications. Plenty of options, but it's difficult for people to make
suggestions without knowing more about your situation.
--
Richard Huxton
Archonet Ltd
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