Re: Loading arrayDS from sql select into statement? -- RPG400-L

Vern/Marvin/Charles,
I was intrigued by the idea of GET DIAGNOSTICS, but at least for my current needs, I too tend to favor opening the process with a "select count(*) into..."
With that, I can wrap the whole "declare cursor", "open cursor", "fetch into", and "close cursor" in an "if countOfRows > 0" structure, thereby not executing unnecessary code when there are no array rows to be loaded.

While this particular need does not require trimming nanoseconds, I was just looking for "best practices" ideas that would enhance my coding, now and future.

Michael Koester

-----Original Message-----
From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Vernon
Hamberg
Sent: Monday, September 14, 2015 5:18 PM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: Re: RPG400-L Digest, Vol 14, Issue 336

Marvin

I thought this was an estimate only for the OPEN - much the same as
SQLERRD(3) which is documented like this for the PREPARE -

For the PREPARE statement, contains the estimated number of rows
selected. If the number of rows is greater than 2 147 483 647, then 2
147 483 647 is returned.

There've been other threads about this, and I think it has been said the
only sure way to get row count is SELECT COUNT(*) FROM TABLE

Now I'm very happy to be mistaken here, because I'd love to have the
simple answer from time to time, the SQLERRD(3) answer. Or the GET
DIAGNOSTICS answer - oh, that array element IS updated with the number or
rows retrieved with FETCH - useful for multiple-row fetches.

I do see that the documentation for DB2_NUMBER_ROWS says it IS the number
of rows after an OPEN or FETCH, but with a SENSITIVE cursor it is an
estimate. I see that default for SENSITIVE on a cursor is ASENSITIVE, so
that what you get depends.

Any takers on whether the GET DIAGNOSTICS value is reliable for managing a
loop? Under what conditions?

Regards
Vern

On 9/14/2015 2:43 PM, Marvin Radding wrote:

Mitch,

There is one method that would be a short cut. GET DIAGNOSTICs can

provide the total number of records in the data set after the open. That
can control the number of records fetched in the FETCH INTO statement.

After the open you can code:

/exec sql
GET DIAGNOSTICS :row_count = DB2_NUMER_ROWS; /end

Marvin

------------------------------

message: 8
date: Mon, 14 Sep 2015 18:17:00 +0000 (UTC)
from: Mitch Gallman <qtemp@xxxxxxx>
subject: Re: Loading arrayDS from sql select into statement?

I've used the following article several times as a reference:

http://www.itjungle.com/fhg/fhg052009-story01.html

I've never had to do a select count prior to doing the fetch.
Mitch

On Monday, September 14, 2015 1:58 PM, "Koester, Michael"

<mkoester@xxxxxxxxxxxxx> wrote:

Charles,

Would be nice if you could use SELECT INTO along with FETCH FIRST XX
ROWS...

After getting the count (select count(*) into :resultCount from...), and

declaring and opening a cursor, I can successfully use

? ? exec sql
? ? fetch MyCursor for :resultCount rows
? ? ? into :ArrayDS;
? ? ? ? ? ? ? ? ? ? ? ?
But there apparently are no shorter shortcuts.

Michael Koester