Re: DBA Question

Hi Booth,

All views are non-keyed which means that when you use a view there is no
guarantee as to the sequence you will get the rows. My understanding (which
has been known to be wrong<g>) is that, since a view does not have an access
path (since you cannot specify an Order By), the Query Optimizer determines
which access path to use at run time - so today you get it in one sequence
but tomorrow it could be different.

Maybe my "little use" comment was over stated but I rarely if ever process a
file in RPG that is not somehow dependant on a key (for a pre-defined
sequence, read between limits or random access).

Sorry Booth, I don't quite understand the comparison with opnqryf.

Paul

----- Original Message -----
From: "Booth Martin" <booth@xxxxxxxxxxxx>
To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
Sent: Sunday, June 19, 2005 6:30 AM
Subject: Re: DBA Question


now I am confused again.  Isn't a non-keyed view treated as a sequential
file?  In this scenario wouldn't a non-keyed view be more similar to an
opnqryf?

---------------------------------
Booth Martin
http://www.martinvt.com
---------------------------------
-------Original Message-------

From: Midrange Systems Technical Discussion
Date: 06/18/05 13:00:45
To: Midrange Systems Technical Discussion
Subject: Re: DBA Question

Hi Jack,

Others have highlighted quite a few of the similarities/differences. My own
view (pardon the pun) is that it depends on how you intend to use them.

If you are talking about developing a DB that will be accessed primarily by
SQL from many different sources, then Views and Indexes. If it is primarily
for RPG, then views, indexes and logical files.

At its simplest, an index is a keyed logical and a view is a non keyed
logical. From an RPG angle the problem is with the views - even they are a
lot more powerful then DDS created logicals they are of little use in RPG
since they do not have a key - so only useful if using embedded SQL.

FWIW, I did an article on comparing DDS and SQL's DDL on search400 at
http://search400.techtarget.com/tip/1,289483,sid3_gci1021854,00.html?FromTax
onomy=%2Fpr%2F2f9

HTH

Paul Tuohy

----- Original Message -----
From: "Jack Derham" <derhamj@xxxxxxxxxxxxx>
To: "'Midrange Systems Technical Discussion'" <midrange-l@xxxxxxxxxxxx>
Sent: Saturday, June 18, 2005 3:40 AM
Subject: DBA Question


> To the List,
>
>
>
> Got into a discussion this afternoon about what the real differences are
> between logical files, views and indexes. The discussion got a little
heated
> at times so I would ask that some of you well versed members to please
help
> out less fortunate uninformed members about the real physical and logical
> attributes of these object types.
>
>
>
> Jack Derham
>
> Direct Systems, Inc.
>
> --
> This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
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>


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