RE: Chain vs SetLL/ReadE

I'm sure this topic will bring many responses. The reason I use Setll
and Reade instead of Chain is I'm never sure what my users will do the
db. Chain returns the 1st record found that matches the keylist values
used is factor 1. In some cases this may not be the record you are
expecting. For example we have a table that hold price information.
The table is keyed by part number and the price effectivity date in
descending sequence. So, one may assume that a chain to the table with
a part number would return the most current price. And it does as long
as no one adds a price record with a future date. I hope this is an
indication why using the setll/reade construct can be better then using
the chain function.


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Chandra Krieg
Sent: Tuesday, September 02, 2008 9:34 AM
To: 'rpg400-l@xxxxxxxxxxxx'
Subject: Chain vs SetLL/ReadE

Hello all,

I have been told that the preferred method of random record retrieval is
to use the SetLL, then do a ReadE and check for the %EOF indicator.

Why is this preferred over using a Chain with %found or even checking
for %Equal on the SetLL before reading the file? I have been told that
the Chain doesn't do what I'm expecting it to but I've never had issues
in the past.

I have read the archive posts and found opinions on the subject but no
concrete explenation as to why. As with some of the posts I don't
understand why you would want to readE the file if the SetLL didn't find
an %equal match or why if you plan to read the file a chain isn't
appropriate.

I'm being told to use the following code instead of a Chain.

SetLL (KeyFields) FIleName;
ReadE (KeyFields FIleName;
DoW Not %EOF(FIleName);
do my stuff
ReadE (KeyFields) FileName;
EndDo;

Any explanations would be helpful!

TIA!

Chandra Krieg
i5 Programmer/Analyst
RateWatch
(P) 1.800.348.1831 ext 311
(F) 1.920.568.1403
www.rate-watch.com