RE: SQL performance question 1

Sorry, there are conditions on the select. I put it in the RPG but not the SQL.

Correction :
Select count(*) from myfile where key = : hostvar and fieldcompared= 'x'

I have advised :

Select key from myfile where key = : hostvar and fieldcompared= 'x' fetch first row only.





-----Message d'origine-----
De : rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] De la part de Michael_Schutte@xxxxxxxxxxxx
Envoyé : jeudi 18 décembre 2008 15:24
À : RPG programming on the IBM i / System i
Objet : Re: SQL performance question 1


Why select a field? Why do a loop?

Either Select '1' into :indicator from myfile where key = : hostvar fetch first row only

Or better

SETLL KEY FILE;
Indicator = %Equal(FILE);




Michael Schutte
Admin Professional
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rpg400-l-bounces@xxxxxxxxxxxx wrote on 12/18/2008 09:16:41 AM:

Hi,

A lot of our developers have recently been introducing SQL into their
RPG code.

We've had a discussion to see how SQL is being implemented.

A lot have replaced this kind of loop:

SETLL key file
dou %eof(file)
READE key file
if %eof
iter
endif

If condition
indicateur = *on
leave
endif
enddo

to see if a row exists, by this :

Select count(*) from myfile where key = : hostvar

I have advised :

Select key from myfile where key = : hostvar fetch first row only.


Is there a better way? Is this a standard way to see if a row exists?
I know there is EXISTS( ) but that would be the same request
(according to visual explain).

Does the RPG version still have any advantages?

Thanks.



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