RE: SQL Problem

[Gord Royle <GRoyle@xxxxxxxx>]

Using "select *" is bad form in any tool and will certainly cause a lot of
grief when you start using cursors. You should never bring back any more
information than is required. If you force the beast to return all (say 500)
fields of a record when you only want two, what will be the impact on
performance(throughput/memory/etc). I know that we all have AS400's with
massive amounts of resources available, but why use them needlessly.

Gord Royle

-----Original Message-----
From: lisa.thomas@Hayssen.com [mailto:lisa.thomas@Hayssen.com]
Sent: Friday, September 14, 2001 2:39 PM
To: rpg400-l@midrange.com
Subject: RE: SQL Problem


I think the key is not necessarily how often your database is changing now
but perhaps how much flexibility you have in rearranging and changing your
database in the future.  The idea behind explicitly listing the fields in
SQL is that if they move the SQL doesn't and shouldn't care.  If you add
fields in the middle of the structure SQL doesn't and shouldn't care.

-----Original Message-----
From: Phil [mailto:sublime78ska@yahoo.com]
Sent: Friday, September 14, 2001 2:34 PM
To: rpg400-l@midrange.com
Subject: RE: SQL Problem


Then also:

select custid from cusmst into :@custid

where custid and @custid are 5A at compile time then custid is changed to
5,0.

If the pgm is not recompiled then there will be a run time error.

Correct?  If so I still don't understand why using * is bad form.  It seems
to me that using embedded sql at all is inherently less safe than using
native I/O.

Personally I have not been in a situation where the database was changed
(other than app's still under development) except for Y2K.  That may be why
I'm having a hard time seeing this.

Phil

> -----Original Message-----
> From: rpg400-l-admin@midrange.com [mailto:rpg400-l-admin@midrange.com]On
> Behalf Of MWalter@hanoverwire.com
> Sent: Friday, September 14, 2001 1:46 PM
> To: rpg400-l@midrange.com
> Subject: RE: SQL Problem
>
>
>
> Regardless of how you change the table, DDS or SQL, if you change the
> structure of the table, and the corresponding host DS is not changed. You
> run the risk of contaminating a field in the data structure.
> Maybe adding a
> field to a table was a bad example. Changing the field length of a field
> might be a better one. Here is a scenario.
>
> You have a table, say: CharField1 10, CharField2, 10, ZoneField1 5,0
> ZoneField2 5,0.
> You write a program specifying your table as the EXTNAME in your hostds.
>
> Now you change the length of CharField2 to 15. You don't compile the
> program. Your host ds still says that CharField2 is 10. When the record is
> fetched into HostDS, wouldn't ZoneField1 contain character data?
>
> Maybe I'm wrong about this. I haven't tried to prove it. If I am, by all
> means let me know.
>
>
> Thanks,
>
> Mark
>
>
> Mark Walter
> Sr. Programmer/Analyst
> Hanover Wire Cloth a div of CCX, Inc.
> mwalter@hanoverwire.com
> http://www.hanoverwire.com
> 717.637.3795 Ext.3040
>
> <SNIP>
>
> You can use ALTER TABLE in SQL to add a field. I THINK,  if  you add a
> field
> using ALTER TABLE and leave it null capable, your existing programs should
> continue to run without any problems.
>
>
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