Re: sql Vs RLA to test existance

Right.

Bad habit of mine, as in our shop, 99% of times we need to check existence
AND retrieve a value, hence the CHAIN. But yes, if you only need to check
for the record existence, I believe SETLL should be faster.

Thanks for the head-up.

Regards,
Luis Rodriguez
IBM Certified Systems Expert — eServer i5 iSeries
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On Tue, Feb 15, 2011 at 10:49 AM, <Tommy.Holden@xxxxxxxxxxxxxxxxxxxxx>wrote:

Using SETLL will outperform the CHAIN as well...

Thanks,
Tommy Holden


From: Luis Rodriguez <luisro58@xxxxxxxxx>
To: "RPG programming on the IBM i / System i" <rpg400-l@xxxxxxxxxxxx>
Date: 02/15/2011 09:17 AM
Subject: Re: sql Vs RLA to test existance
Sent by: rpg400-l-bounces@xxxxxxxxxxxx



In the SQL vs RLA contest, if you are using the SQL example below just for
checking records, RLA should win in performance, as the process of
Validating the query, optimizing it (creating an Access Plan) building the
ODP, etc is very expensive in time terms, compared to a simple CHAIN,
where
practically the only overhead is when you OPEN the file.

Regards,
Luis Rodriguez
IBM Certified Systems Expert ? eServer i5 iSeries
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On Tue, Feb 15, 2011 at 10:27 AM, Luis Rodriguez <luisro58@xxxxxxxxx>
wrote:

David,

IIRC, EXISTS stops as soon as it finds the first record. The syntax is:

SELECT * FROM TABLE1 WHERE EXISTS(SELECT 1 FROM TABLE2 WHERE

TABLE1.FIELD

= TABLE2.FIELD) ;

Regards,
Luis Rodriguez
IBM Certified Systems Expert ? eServer i5 iSeries
--




On Tue, Feb 15, 2011 at 10:14 AM, David FOXWELL

<David.FOXWELL@xxxxxxxxx>wrote:

Hi,

I need to find if a transaction of a particular type and amount exists

for

a client.

I cannot remember how to apply the SQL Exists( ) to look for the
transaction.

Select '1' from ???? where exists ( select * from mytable where myfield

=

'myfield')


Then again, I seem to remember that EXists will scan all the rows and

not

just stop at the first one that satisfies the search criteria as I

could do

with RLA.

Can someone put me straight please?

Thanks.

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