• Subject: Re: PF File Definition questions...
  • From: Pete Hall <pbhall@xxxxxxxxxx>
  • Date: Sun, 24 Oct 1999 20:25:12 -0500

At 20:08 10/22/1999 , you wrote:
> > Views are unkeyed logical files....
>Huh?  Now I'm confused...   There's no -point- in having and unkeyed logical.
>The Key is the index sequence.  Gotta have one.

Au Contraire. The VIEW is very useful, but only for manipulating data with 
SQL. INDEXes provide the access paths. They can only be attached to a 
physical file. SQL will examine the WHERE, JOIN and ORDER BY clauses in 
your query, and select the appropriate access path (index), or build a 
temporary one if necessary. A VIEW describes data elements, where the data 
comes from, what transformations are to be performed on it when it is 
retrieved, and what relationships are required with literals or other 
column values. A VIEW can be based on one or more physical files or other 
views, and can contain grouping functions such as SUM, MAX and MIN, as well 
as calculations, conditional expressions and special register values like 
USER, CURRENT DATE and CURRENT TIME. It's even possible to build a pivot 
table as a view of transactional data and have it perform reasonably well. 
You can do lots of really slick stuff that a few years ago would have 
required a work file and a HLL program.
Pete Hall
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