Re: can I use sum with computed by

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#80

From: Isaac
Date: Tue, 27 May 2008 23:08

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Bill Todd [TeamB] wrote:
> Isaac wrote:
> 
>> sorry I was not quit clear I want the contrary I want to use select
>> sum() to return the computed by value
> 
> I do not recall if that  will work or not but it is a very bad idea.
> The SELECT SUM will run _every_ time the record is accessed whether you
> need the sume or not. This is likely to cause poor performance.
> 
ok speaking of performance Mr Maxim tell me a good way to get two sum 
values with for select ...

for
   select field_a, sum(field_b)
   from t
   group by field_a
   into :v_a, :v_sum_b
do begin
   if (v_a) = 1 then some_var_1 = v_sum_b;
   else if (v_a) = 2 then some_var_2 = v_sum_b;
   /* and more if's if ther are more distinct values in field_a */
end


is this better in performance (for a stored procedure) than using 2 Selects

ex:

select sum(f) from tab1 where f2 = 1

Thanks
select sum(f) from tab1 where f2 = 0

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