RE: SQL logical file equivalent

Hi Darrell

As the original post asked for the equivalent, here you go. In SQL a view gives you the subset of fields. An index gives you the key. So you would use a select over the view with an order by that corresponds to an index key.

Now you cannot have both view and index combined in one object in SQL - that is where non-SQL logicals have an advantage when using F-specs and native RPG op-codes. You CAN use a view in RPG, as well as an index, but you get one or the other, as has been said already, I think.

HTH
Vern

At 06:55 AM 4/20/2007, you wrote:

Hi:

We use DDS-defined "reduced logicals", as described -- with a different
record format name and a specific, limited number of fields included --
for a variety of reasons. They are not only useful for avoiding level
checks, they also avoid reading unmanaged field values into a program. A
reduced logical with only a few fields selected from the physical, and
with all fields renamed in the program, can be used as a lookup table even
at a point where the base physical file (or another logical that sorts the
physical and includes all fields) has a completely different record
locked. That's just one example.

Darrell

Darrell A. Martin - 630-754-2141
Manager, Computer Operations
dmartin@xxxxxxxxxxxxx

midrange-l-bounces@xxxxxxxxxxxx wrote on 04/19/2007 07:29:08 PM:

> "
>
> But that's an important distinction. If you create a DDS LF and name the
> fields those are the only fields in the lf, even if you add more to the
> table. However, the LF created from an index will change automatically
> to have any new fields in it. So if you're using that LF in a 3GL you
> need to be worried about level checks.
>
> One of the great things about SQL is the ability to add columns w/out
> regard to level checks. Don't break that by using indexes in 3GL
> programs for RLA.
>
> "
>
>
>
> But so will a regular logical file.
>
>
>
> If I create a logical file over a physical file and just use the record
> name equal to the record name of the physical file (which 99% of the
> people do) and I add a field to the physical file using CHGPF , the
> logical file will get the new field.
>
> If I create the logical with record name different from the physical
> record name and list the fields I want to include in the logical, and I
> add a field to the physical using CHGPF, the new field will not show up.
>
> So the behavior is no different if you go into operations navigator and
> add a new field to a table. It will appear on the logical associated
> with the index.
>
> Of course, it makes no sense to me know days to use a logical or
> physical record I/O unless I have to. I think this got started because
> the person had a case tool that won't use SQL statements and has to have
> a physical or logical file. Yuck!!
>
>
>
> Probably 99% of my coding today is done using SQL.