Re: MIDRANGE-L Digest, Vol 3, Issue 1075

[Joel Cochran <jrc@xxxxxxxxxx>]

On Fri, 2004-07-23 at 17:00, midrange-l-request@xxxxxxxxxxxx wrote:
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> Today's Topics:
> 
>    1. RE: SQL vs. traditional I/O? (Jim Essinger)
>    2. archiving  delaying (Muralidhar Narayana)
> 
> 
> ----------------------------------------------------------------------
> 
> message: 1
> date: Fri, 23 Jul 2004 10:48:27 -0600
> from: Jim Essinger <esinger@xxxxxxxx>
> subject: RE: SQL vs. traditional I/O?
> 
>    At 10:16 AM 7/23/2004, Rob wrote:
> 
>      The ONLY advantage DDS has over SQL is the ability to combine an index
>      with
>      a view.  Or, in DDS terms, the ability to create a logical file with
>      field
>      and/or record selection and a key.  However this is only an advantage in
>      traditional I/O.  In SQL I/O you would read the 'view' or the file with
>      the
>      field and/or record selection.  And the optimizer would use the
>      appropriate
>      'index' to find the best key.
> 
>    The other thing that DDS _can_ bring to the table is using field reference
>    files, if you design your files that way.  Not do-able in SQL if I
>    remember right.
> 
>    Jim

Actually, you can.  They are called UDFs or "User Defined Datatypes". 
Let's say you want to have a field for "OrderTotal".  You can define a
type for other SQL statements to use called "OrderTotal" and define it
as a "numeric(10,2) not null with default".  Now when I create a table,
I give the appropriate field the type of "OrderType".

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.

Joel
http://www.rpgnext.com