RE: Normalization was Left AS/400 and Returned

True, but that technique won't get you a listing sorted by customer number 
and part number out of
orderhead
ordernbr   customernbr
001        001
002        003
003        005
004        001

orderline
ordernbr  linenbr   partnbr
001       001       ABC
001       002       ZYX
002       001       TGH
004       001       ABC
004       002       CDE

Rob Berendt
-- 
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





michael@xxxxxxxxxxxxxxxxxx 
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05/03/2005 02:08 PM
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Subject
RE: Normalization was Left AS/400 and Returned






Of course, a lot of RPG programmers don't use join logicals. Instead,
they provide their own indexed file navigation by getting a value from
one file, using that value to chain to another file, getting value from
that file, chaining to another file...and on and on. There's a divide in
AS/400-land...those that can/will use SQL or join logicals and want a
normalized database, and those who have a series of indexed files and
do their own navigation. Basically, if a programmer wants to use more
modern techniques, the iSeries can support them. And of course, if a
programmer still wants to code in RPG/II, they can. The ability to use
30 year old techniques is a 'feature' on the iSeries.


> -------- Original Message --------
> Subject: Re:  Normalization was Left AS/400 and Returned
> From: rob@xxxxxxxxx
> Date: Tue, May 03, 2005 2:55 pm
> To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
> 
> I agree on the multi-format and join logical files.  Or, SQL's views. 
And 
> highly recommend them for programming, and, most especially, for common 
> links the users use in Queries instead of having them join multiple 
files 
> together.
> 
> However, he might be right about the performance issue.  For example, 
> which would access faster:
> 1 - A key over customer number and part number in a de-normalized 
> order/line file.
> 2 - A join logical that joins the order/header file with the order/line 
> file so that you can see the customer number from the order header file 
at 
> the same time you see the part number of the order line file.  And, keep 

> in mind, that a join logical file does not allow keys from more than one 

> file, even though I suspect every new release of OS/400 has formed yet 
> another DCR requesting this feature.  This might be possible with an 
index 
> on a view in SQL but I don't think that's allowed either.  I know you 
can 
> get the data this way in a normalized database via SQL but it's going to 

> do some work under the covers and performance may suffer.
> 
> Rob Berendt
> -- 
> Group Dekko Services, LLC
> Dept 01.073
> PO Box 2000
> Dock 108
> 6928N 400E
> Kendallville, IN 46755
> http://www.dekko.com
> 
> 
> 
> 
> 
> "Bill Meecham" <bmeecham@xxxxxxxxxxxxxxxxxxxx> 
> Sent by: midrange-l-bounces@xxxxxxxxxxxx
> 05/03/2005 01:33 PM
> Please respond to
> Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
> 
> 
> To
> "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
> cc
> 
> Subject
> Re: Left AS/400 and Returned
> 
> 
> 
> 
> 
> 
> That's not necessarily true since multi-format and join logical files 
can 
> be created and created much easier when the database is normalized.  The 

> reason shops don't normalize is more likely because it's difficult to 
> master and there is little perceived benefit.  Borrowing from another 
> thread, that's a large part of what case tools help 
with....normalization 
> and 'virtualization' of fields. 
>   ----- Original Message ----- 
>   From: michael@xxxxxxxxxxxxxxxxxx 
>   To: Midrange Systems Technical Discussion 
>   Sent: Tuesday, May 03, 2005 2:25 PM
>   Subject: RE: Left AS/400 and Returned
> 
> 
>   The reason that most vendors and shops don't have normalized databases
>   is because most vendors and shops don't use the data store on the
>   iSeries as a database - it's used as a system of indexed files.
>   Normalization in that scenario can hurt performance, because the
>   program would need to chain to several files to gather the information
>   needed to present to the user. There's no doubt that normalization is 
a
>   good thing for a database (at least 3NF), but normalization for 
indexed
>   files isn't as important or desired.
> 
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