Re: SQL dates and numeric columns

Seems to me there could be a pretty fast technique using a data area with 2 instances of the same date, so 12 long for 6-digit dates. If that date is YMD, then MDY is at POS(3), that's a 3rd subfield. If that date is MDY, then YMD is at POS(5), so that's a 4th subfield. "Conversion" is probably almost instantaneous.

Now trouble might still be, you'd better comment it up to the heights, for maintainability.

This is an example of something that is basically rotation - like rotating bits in C. We don't have a rotate BIF or operation. There are shift MI operations, which should be quick - but I don't know how one makes a shift into a rotate - rotate left of 16 or 32 bits would convert one way or the other, I think.

Yes, I know - what in the world have I been drinking, right? Orange mango sparkling ice at the moment!!

Cheers
Vern

On 9/5/2023 9:41 PM, Roger Harman wrote:

YMD MULT 100.0001 MDY
MDY MULT 10000.01 YMD

Leveraging some quirk in the system to do date conversions.
I remember first seeing this and just shaking my head.
But it was pervasive.

Roger Harman
COMMON Certified Application Developer - ILE RPG on IBM i on Power



-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Vern Hamberg via MIDRANGE-L
Sent: Tuesday, September 5, 2023 5:37 PM
To: midrange-l@xxxxxxxxxxxxxxxxxx
Cc: Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx>
Subject: Re: SQL dates and numeric columns

Hey Jim, wasn't there the old RPG chestnut of multiplying by 1000000 of
a couple numbers in a data structure? Another "cute" trick,
unmaintainable, and a dog as to performance.

I might have the exact details off, but it's no longer the think to do.

Cheers
Vern

On 9/5/2023 10:01 AM, Jim Oberholtzer wrote:

The reason those calculations work is (presuming the fields are set to 6
char) they cause arithmetic overflows and exceptions the system is smart
enough to ignore. While the code may be somewhat shorter, it's not
intuitive, only the initiated would understand it, and it performs
horribly. While the SQL and several other methods of date management might
not be as short, they perform better and in the end far more maintainable.
None of my customers allow that type of date manipulation anymore. That
fad went out of style back in the very early 2000's. While more verbose,
time to use modern methods.

--
Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On Tue, Sep 5, 2023 at 9:42 AM Dave <dfx1@xxxxxxxxxxxxxx> wrote:

I'm surprised it's still so difficult to get a date from a numeric value
Concat gives me this horrendous code :

date(

concat(

concat(

concat(trim(char(Y)), '-'), concat(trim(char(M)), '-')

)

, trim(char(D)))) " MyDate "

I would have liked to have been able to use
Y* 10000 + M* 100 + J



---------- message ---------
From: Dave <>
Date: Fri, 1 Sept 2023 at 10:40
Subject: SQL dates and numeric columns
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>


Hi,



Trying to do date operations on a physical file where the date is coded in
3 different numeric fields Y, M and D



1 - I created a view, can I do better than this :

date(trim(char(Y))!!'-'!!trim(char(M))!!'-'!!trim(char(D))) "MyDate"

?


2 – This works in an SQL session but the RPG compiler doesn’t seem to like
the ‘ !’ character. Any ideas ?



Thanks
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