Re: Repeated CLOSE and OPEN of SQL cursors

Very good point. The biggest single error that RPG programmers make with
SQL is not error checking each SQL statement.

In this case, you need to check the Prepare, Open and Fetch statements for
errors each time.

For prepare,
Exec Sql Prepare stmt
If SqlState <> SQL_STATE_OK; // '00000'
Throw error
EndIf.

Open the same thing.
Exec Sql Open Cursor
If SqlState <> SQL_STATE_OK;
Throw error
EndIf;

On a fetch

Exec Sql Fetch Next
From cursor
Select;
When SqlState = SQL_STATE_NO_ROW; // '02000'
// close cursor processing.
Return or leave.
When SqlState = SQL_STATE_OK;
// Ok processing.
Other;
// Throw error.
Endsl;

On Mon, Oct 10, 2022 at 7:10 AM Daniel Gross <daniel@xxxxxxxx> wrote:

Hi Alan,

what Darren wrote is often true - especially when you only code

dow SQLCODE = *zero;
...

Because loops like that are do not detect SQL errors (SQLCODE < *zero).

The best way is, to step debug the program, and find out, what happens.

And of course - you have to make sure, that the SFL is cleared and RRN is
reset when starting over.

Regards,
Daniel

Am 10.10.2022 um 16:04 schrieb Darren Strong <darren@xxxxxxxxx>:

Usually this happens because there is one or more values that you

cannot bring into your program because the value is not compatible with the
variable. For example, if one field is sometimes null, and your RPG
variable can't except a NULL, then the SQL fetch fails, you get a code that
you assume is the end of the list code, and your Dox loop exits. When you
sort (order by) the list, these nulls come at different times in the cursor
fetch.

-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Alan

Cassidy

Sent: Monday, October 10, 2022 9:26 AM
To: rpg400-l@xxxxxxxxxxxxxxxxxx
Subject: Repeated CLOSE and OPEN of SQL cursors

CAUTION: This email originated from outside of the organization. Do not

click links or open attachments unless you recognize the sender and know
the content is safe.

I have one last thing stumping me for now to finish a major code change

to boost performance in one program I'm working on, relating to SQL cursors.

The RPG program opens an SQL cursor and the entire subfile is input.
Then the user requests a different "ORDER BY" than the default. I use

the same SQL for the sort, the whole thing is identical except for tacking
on the different ORDER BY clause at the end of the dynamically constructed
SQL statement.

At the top of the subroutine that does the cursor open, the code first

does an Exec SQL Close M1, where M1 is the cursor. Then re-open. So if this
is the second or third time, etc., opening the cursor, the code first runs
the line "exec SQL Close M1".

The issue is that the sorted open is getting sometimes around two or

three times (it varies) as many rows returned as the first open.

Can someone point me to why or how that could happen?

--Alan Cassidy



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