Re: Function use in query

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От Ioana Danes
Тема Re: Function use in query
Дата
Msg-id 1370525524.12482.YahooMailNeo@web164606.mail.gq1.yahoo.com
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Ответ на Re: Function use in query  (David Johnston <polobo@yahoo.com>)
Ответы Re: Function use in query  (David Johnston <polobo@yahoo.com>)
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Ioana Danes wrote

> Hi All,
> Is there any similar syntax that only invokes the procedure once and
> returns all the columns?

Generic, adapt to fit your needs.


WITH func_call AS (
SELECT function_call(...) AS func_out_col
)
SELECT (func_out_col).*
FROM func_call;

Basically you have to execute the function call and leave the result as a
single column (a row type).  Then, in another layer of the query, you expand
that single column into its components using "*".  Because you are expanding
a column and not a table you must put the column name in "()" - otherwise
the parser thinks "func_out_col" is a table and errors out.

This all definitely applies to 9.2 and earlier.  9.3 (with lateral) may
behave differently...

David J.

Hi David,

Thank you for your reply, I haven't thought about it. This works as expected if I don't need to filter the table
tmp_Cashdrawer:

select tmp_Cashdrawer.CashdrawerID,
(test1(tmp_Cashdrawer.CashdrawerID)).* from tmp_Cashdrawer where
tmp_Cashdrawer.CashdrawerID in (1);

If I will have to filter the  tmp_Cashdrawer table then it executes the function for the all the cash drawers and then
filterout the result which again is not efficient... 

I might use an aggregate table for this. This way I can use a simple function call to update the aggregate table when a
cashdrawer is balanced or before executing the report.  

Thanks again for your reply,
Ioana


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