Re: SQL performance question 1

First off,

If you're trying to replace RPG op-codes directly with their SQL
equivalent, you're going down the wrong path.

Performance will suck, and you've not added any value to the process.

You really need to re-write the app to take advantage of SQL's
set-at-a-time nature instead of RPG's record-at-a-time.

Charles



On Thu, Dec 18, 2008 at 9:16 AM, David FOXWELL <David.FOXWELL@xxxxxxxxx> wrote:

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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