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

["Paul Tuohy" <tuohyp@xxxxxxxxxxxxx>]

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.
>