RE: SQL Date Math

["Don Cavaiani" <dcavaiani@xxxxxxxxxxxxx>]

In System i5 Query (WRKQRY) I do the following:
------------------------------------------------
Result fields:

Today    	current(date)
Todaychar	char(today)
Today2	'20' || substr(todaychar,7,2) || substr(todaychar,1,2 ||
substr(todaychar, 4,2)
Refdta	digits(refdt)
-------------------------------------------------
Then:

In Select Test:

	refdta	LE	today2
--------------------------------
How would I do the same in SQL?


 

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Wednesday, November 14, 2007 10:27 AM
To: Midrange Systems Technical Discussion
Subject: Re: SQL Date Math

One last time trial...
Instead of something like
select * from ...
where myNbrDate>CvtDateToNumISO(...)
Try:
select * from ...
where CvtNumISOToDate(myNbrDate)>...
Which will really tell us why you hose up the index by converting the
file data to the input data instead of converting the input data to the
file data.

Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





"Michael Ryan" <michaelrtr@xxxxxxxxx> 
Sent by: midrange-l-bounces@xxxxxxxxxxxx
11/14/2007 08:30 AM
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Re: SQL Date Math






That was interesting. Here are the results.

All run in interactive SQL, approximately 56M records. Index built
over the numeric field (which took a freaking long time btw - like 10
minutes).

Using CvtDateToNumISO function with no index - 45 seconds
Using function code with no index - 38 seconds
Using CvtDateToNumISO function with index - 11 seconds
Using function code with index - 2 seconds

On Nov 13, 2007 7:05 PM, Michael Ryan <michaelrtr@xxxxxxxxx> wrote:
> Yes...going from date to numeric. I just named it backwards to throw
> off the opposition. :)
>
> Sure...I'll give it a go first thing in the morning, and I'll post my
> results back here. I'll also create an index over the numeric field
> and see how that helps things.
>
> On Nov 13, 2007 5:28 PM, Elvis Budimlic
>
> <ebudimlic@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Michael,
> >
> > Do you mean CvtDateToNumISO?  Going from DATE to NUMERIC, not the 
other way
> > around.
> >
> > If so, do you mind running another test?
> >
> > Take Charles' code out of the UDF and put it in the SQL statement 
itself.
> > Then run it.
> > I'm curious to see if UDF call itself contributes any significant 
overhead.
> > BTW, do you have an index over the numeric(8,0) field?
> > If not, I think it would be worth running a test again after you 
create one.
> > Elvis
> >
> > Celebrating 10-Years of SQL Performance Excellence on IBM i5/OS and 
OS/400
> > http://centerfieldtechnology.com/training.asp
> >
> >
> > -----Original Message-----
> > Subject: Re: SQL Date Math
> >
> > Charles' CvtNumtoDateISO function works swell! It takes 120 seconds
> > for my query (56M records) using the date and substr method, and 39
> > seconds for the CvtNumToDateISO method. And that's on the
development
> > system. Much faster on the production system.
> >
> >
> >
> >
> > --
> >
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