RE: CREATE INDEX and name only some columns

Rob,

What release was that on?

For my test on v5r2, I was using an internal DS.

Charles

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Wednesday, September 12, 2007 10:52 AM
To: Midrange Systems Technical Discussion
Subject: RE: CREATE INDEX and name only some columns

Charles, a really nasty appeared regarding the select *
into... when you were using an external DS. If you added
fields to the file and did not recompile (thus changing your
external DS) it used to just happily ignore the extra fields
at the end. Then IBM came out with a new release that
decided that was a bad idea and had the program drop to it's knees.

Anyone hear the myth about being able to put on new releases
and having 100% code compatibility on i5/os, unlike Windows?

Rob Berendt
--
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Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





"Wilt, Charles" <WiltC@xxxxxxxxxx>
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RE: CREATE INDEX and name only some columns






Waldon,

Actually, I was under the apparently mistaken impression that
you would
have to recompile since you'd
be changing the number of columns being returned and thus the
number of
variables you'd need to hold
the returned data.

However, a quick test shows that at least with a SELECT INTO
that doesn't
appear to be the case; but
only as long as the column is added to the end of row.

RPG retrieves data by ordinal position in the results set, it
apparently
doesn't care if there's more
columns than it was expecting.

Dropping a column would be a bad idea; but probably not a
real concern.

Somewhere, someone said that using SELECT * in a production
application
was a bad idea. IIRC, that
was a recommendation to follow no matter what DB or what language was
involved but I thought it really
was applicable to RPG. A quick google search, turns up at least one
result. The following reasons
apply to using SELECT * and any DB and language:
1) extra unneeded data returned
2) doesn't allow index-only access
3) Stability - applications could be accessing via ordinal position
instead of column name.

Point 3 is the is important to us since RPG with embedded SQL
always uses
ordinal position.

So I've learned that SELECT * doesn't have to mean a recompile, but I
think I'll still continue
specifying specific columns names in most cases.

Charles

-----Original Message-----
From: midrange-l-bounces+wiltc=cintas.com@xxxxxxxxxxxx
[mailto:midrange-l-bounces+wiltc=cintas.com@xxxxxxxxxxxx] On
Behalf Of Walden H. Leverich
Sent: Tuesday, September 11, 2007 6:59 PM
To: Midrange Systems Technical Discussion
Subject: RE: CREATE INDEX and name only some columns

1) Better performance
2) You can change the DB without needing to recompile all

the program.

I'm with you on #1 & #2 for DDS/LF, but since you say "same
reason you'd..." you seem to imply that both cases are true
in SQL too. I can see #1, but #2 isn't true, is it? If I
"select * from..." in an RPG program I can still change the
underlying table w/out a recompile, can't I?

-Walden

--
Walden H Leverich III
Tech Software
(516) 627-3800 x3051
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)


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