Seems to me that you're going to spin through a LOT fewer records by keying
on OrderID first in this example and, then, looking for the date.
Your subset of OrderID's is much narrower, one would assume, than subsetting
by date ranges.
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Klugman, Luke
Sent: Thursday, April 11, 2013 8:38 AM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: RE: Logical file in RPG
An example of my situation is that I have an order file, say with an orderId
and orderDate field.
I may receive 50 million orders a year, and I want to be able to check
whether I have previously received the same order within the last year.
I know I can just create a logical on orderId and check, but just wanted to
know if there was a way of sub setting my file by for instance current ytd,
and then checking for my orderId.
Kind rgds
Luke
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Anderson, Kurt
Sent: 11 April 2013 15:48
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: RE: Logical file in RPG
Create a new index?
I don't understand this line of thinking. If I was concerned about all the
different fields we may want to access a file by I'd never get any indexes
created - or they'd end up convoluted and inefficient. Is it that any new
index would want to also select only a subset of records?
If so, then each new index may need a new view (as Gene gave an example
of) if you want the database to be the one supplying a subset of data
(instead of needing programs to do it).
I guess if you provided an example of a possible situation you're concerned
about, I (and possibly we) could better visualize your concern.
-Kurt
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Klugman, Luke
Sent: Thursday, April 11, 2013 9:19 AM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: RE: Logical file in RPG
Thanks for this Gene, but what if I have an additional field I want to use
as the key, instead of the date...
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Gene Burns
Sent: 11 April 2013 14:36
To: RPG programming on the IBM i / System i
Subject: Re: Logical file in RPG
You could create the index over the table using the date then create a view
over the table with the date selection. If I recall correctly the view
would utilize the index to select the correct data.
CREATE INDEX ATABLEI1 ON ATABLE (DATE_FIELD)
CREATE VIEW ATABLEV1 ON ATABLE
WHERE DATE_FIELD >= (CURRENT DATE - 1 YEARS)
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