Re: Use of DDS field names in RPG -- RPG400-L

Even better...

select a.key1, a.key2, a.somefield, b.otherfield
from fileA A join FileB B using (key1, key2)

Of course the JOIN USING syntax is slightly broken at v5r4.

The standards call for the result set to include only one set of the
key fields..so you aren't supposed to need the qualification..

select key1, key2, a.somefield, b.otherfield
from fileA A join FileB B using (key1, key2)

This is fixed at 6.1

It's not to big a deal unless you want to do multiple joins with the
USING syntax..

from (fileA A join FileB B using (key1, key2))
join FileC C using (key1, key2)

note: parens add for clarity

The above won't work at v5r4 but will at 6.1 as the result of the join
between FileA and FileB includes only one Key1 and key2 fields.

HTH,
Charles

On Mon, Sep 28, 2009 at 9:23 AM, <rob@xxxxxxxxx> wrote:

<snip>
If I only had to code for VRM540 and above I would probably drop the
prefix and use PREFIX to map file field names to qualified data
structures.
</snip>

Amen brother. We had a vendor package that even many releases ago would
use the same field name in all files. For example, if it was ITEMNBR then
it would be ITEMNBR in all files, not AAITEMNBR, BBITEMNBR, etc. Even
though all programs had to manually use I specs to rename the columns
(think RPG/400 not RPGLE). Now it's so easy with PREFIX and QUALIFIED
that there's no need to keep them all separate. Even ancient tools like
Query/400 support T01.ITEMNBR, T02.ITEMNBR.

And it sure makes it easy to find a field by using
SELECT SYSTEM_COLUMN_NAME, SYSTEM_TABLE_NAME, SYSTEM_TABLE_SCHEMA
FROM syscolumns
WHERE system_column_name='ITEMNBR'

Try that on your system.

ps: What's DDS? :-)

Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com

From:
Simon Coulter <shc@xxxxxxxxxxxxxxxxx>
To:
RPG programming on the IBM i / System i <rpg400-l@xxxxxxxxxxxx>
Date:
09/28/2009 07:02 AM
Subject:
Re: Use of DDS field names in RPG
Sent by:
rpg400-l-bounces@xxxxxxxxxxxx

On 28/09/2009, at 6:18 PM, David FOXWELL wrote:

Although, I realise the limitations of this. I can't use EVAL-CORR
while I have this kind of prefix.

You can use PREFIX creatively on both the file definition and the data
structure definition to remove the first character from the field
name. Used in conjunction with QUALIFIED data structures you should be
able to use EVAL-CORR quite happily.

What kind of field naming standards are you using in DDS?

I generally use a 2-character file prefix with up to 8 characters for
the field identifier itself. I also specify a meaningful ALIAS for SQL
access. Six character field names (as in your convention) are no
longer needed with RPG IV.

The only reason for the prefix is RPG's insistence that each field
name refers to a single storage location. Languages that support
qualification (e.g., COBOL and C) don't need this sort of work around.

If I only used SQL for data access I would drop the prefix. If I only
had to code for VRM540 and above I would probably drop the prefix and
use PREFIX to map file field names to qualified data structures.

Regards,
Simon Coulter.
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