Re: SQL and defining data structures

Hello Birgitta,

Will you have to create the view again, if you change one or more of the
files behind the view? For instance adding one or more fields to a file.

Best regards

Jan


Am 31.08.2017 um 07:21 schrieb Birgitta Hauser:

This happens not often, but this time I agree with Dieter.

Create a view based on the complete select statement (with the exact
field selection you need and including all Common Table Expressions, Joins,
Group Bys, Nested-Sub-Selects etc. - without the Order By).
The view cannot only be used for accessing the data, but it can be
included as external data structure.

In your program you define the view as external data structure.
In the Declare Statement you specify a simple SELECT * FROM VIEW (may be
with several additional WHERE conditions and an ORDER BY clause).
In your FETCH statement you fetch the data directly into the external
data structure.

No need to create an additional file with all the fields or a data area
or what ever.
BTW a view is never keyed, it is nothing else than a stored select
statement. In this way you theoretically can have thousands of views on
the same table without any performance impact.
... and a view can be used where ever you use a table or physical file,
e.g. embedded SQL, ODBC, JDBC, Download to Excel, WebQuery and even
Query400 etc.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

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-----Original Message-----
From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Joe
Pluta
Sent: Donnerstag, 31. August 2017 03:08
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: SQL and defining data structures


My one unbreakable rule is that there are no unbreakable rules.

I've been doing quite a bit of research recently in the area of
mitigating change impact in 24/7 shops. It's been a revelation. When using
an externally described data area as a reference file (as in my
example) there is no more linkage to the file definition than if you
compiled over a view. So yes, you're referencing the file, but no, you're
not in danger of a level check.


... create view is your friend. You must not reference any file in

your programms anyway, never ever.

D*B

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