RE: Views and Indexes (was Re: MIDRANGE-L Digest, Vol 3, Issue 1075)

[<Rick.Chevalier@xxxxxxxxxxxxxxx>]

Paul,

<snip>
Only SQL defined indexes are really accessible by traditional I/O - which means 
you
can't make use of all those cool features that were defined in views (without 
using embedded SQL).
<snip>

I don't believe this is correct.  I have used an SQL view as in input file 
defined on the F-spec without any other SQL in the program.  Maybe I'm not 
understanding what you are saying.

Rick

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx]On Behalf Of Paul Tuohy
Sent: Friday, July 23, 2004 2:37 PM
To: Midrange Systems Technical Discussion
Subject: Views and Indexes (was Re: MIDRANGE-L Digest, Vol 3, Issue
1075)


Hi Joel,

I think the clarity needs some clarification :-)

You are correct that views have columnar abilities (quite a lot of them)
that are not available in DDS but views and indexes are two very seperate
things.

A view does NOT incorporate an index. When using a view (using SQL select)
it is the ORDER BY CLAUSE and WHERE clauses that are used to determine which
index is used.

A logical file is not just an index. It can do sequence, selection,
projection, union and join - just not as many options as SQL. It's one big
advantage (as Rob pointed out) is that a logical file can define a combined
view and index. This is of enormous value for traditional I/O. Only SQL
defined indexes are really accessible by traditional I/O - which means you
can't make use of all those cool features that wer defined in views (without
using embedded SQL).

Paul Tuohy


----- Original Message -----
From: "Joel Cochran" <jrc@xxxxxxxxxx>
<snip>
> And for clarity, a View incorporates an index.  A view has columnar
> abilities that are not available in DDS.  A view is more than an index,
> where as a logical file, no matter how complex, is just an index.  A
> view is limited to the subfields mentioned within.
>


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