What's the correct way to check sql found condition in ILE RPG? - rpgle

Question

When working with embedded SQL in RPG, you often end up with a cursor and a dow-loop for processing all rows in your result. The condition in the loop is somehow dependent on SQLCOD and/or SQLSTT, some globally available variables in an SQLRPGLE-program?
But what is the correct way of checking these values? Some suggest SQLCOD = 0 others not (SQLCOD = +100 or SQLSTT = '02000'). One fails on all warnings, the other does not fail on some errors, so I'm not content.
To illustrate what I do with some code:
Pmain B
D PI
Dmy_ds E DS extname(SOME_TABLE)
D qualified
/free
exec sql
DECLARE cur CURSOR FOR
SELECT *
FROM some_table;
exec sql
OPEN cur;
exec sql
FETCH cur
INTO :my_ds;
dow sql_found();
exec sql
FETCH cur
INTO :my_ds;
enddo;
exec sql
CLOSE cur;
/end-free
Pmain E
Psql_found B
D PI N
/free
// insert return statement here...
/end-free
Psql_found E
I'm looking for the correct return statement here, that will make me go through all rows if no error occurs and lets me leave when an error occurs. Bonus points for some decent way to check for errors.

Answer 1

SQLSTATE is better, and recommended by IBM.
From IBM's InfoCenter SQL Messages and Codes Reference: SQLCODE and SQLSTATE concepts
SQLSTATE is the preferred standard return code.
SQLSTATE is 5 characters, with the first two bytes identifying a class of conditions.
'00' = Unqualified Successful Completion
'01' = Warning
'02' = No Data
Anything else is an error. I generally only check for '00'.
Simple. Easy. More portable.
Using SQLCODE often involves lists of codes which are, IMHO, less than developer friendly.
Example:
Personally, I generally include definitions and code like this:
D xSQLState# s * inz( %addr(SQLState) )
D xSQLState ds 5 based(xSQLState#)
D xSQLState2 2a
D
D Success_On_SQL C const('00')
D Warning_On_SQL C const('01')
D NoData_On_SQL C const('02')
Then after any SQL operation, I generally check
if xSQLState2 <> Success_On_Sql;
someflag = true;
endif;

Answer 2

The best practice is to process the SQLCODEs you expect (as part of the expected processing) and to add exception code to handle the ones you don't. One implementation:
dow 1=1; // forever
exec sql
FETCH cur
INTO :my_ds;
// normal exit
if sqlstt = SQL_NODATA;
SFLEND = *on;
leave;
endif;
// can't CAST a value
if sqlstt = SQL_CAST; // CAST error
... tell user there's an error and read another
iter;
endif;
// decimal data error
if sqlstt = SQL_DDE;
tell user to call IT and stop reading
leave;
endif;
// whoops! not expected at all. Dump for post-mortem
if sqlstt <> SQL_NORMAL;
... tell user to call IT and stop reading
dump(a);
leave;
endif;
// test for end of loop
// filled subfile page?
enddo; // forever
With this type of implementation you have to intentionally leave the loop; whether you've filled a subfile page, loaded the highest element in an array or hit an error. I'm not sure there is a single, generic implementation that will handle all circumstances. Sometimes you might want to leave the read loop if you have a record lock and sometimes you want to issue a message and try again (for example).

Answer 3

I did some more searching on the topic and found something on IBM's site (quote):
The SQLCODE is also set by the database manager after each SQL
statement is executed as follows:
- If SQLCODE = 0 and SQLWARN0 is blank, execution was successful.
- If SQLCODE = 100, no data was found. For example, a FETCH
statement returned no data, because the cursor was positioned
after the last row of the result table.
- If SQLCODE > 0 and not = 100, execution was successful with a
warning.
- If SQLCODE = 0 and SQLWARN0 = 'W', execution was successful
with a warning.
- If SQLCODE < 0, execution was not successful.
Which would lead me to an sql_found() like this:
Pfound_sql B
D PI N
/free
return (SQLCOD >= 0) and (SQLCOD<>100);
/end-free
Pfound_sql E
That should take care of the End of Data condition and fail on all errors. I'm not sure if there are some warnings that I should take care of (don't want to get trapped in an endless loop, if there is a warning that leads to not reading).