如何使用Perl DBI检索DB2 SQL sproc的返回值？

Question

I need to retrieve the value returned by a DB2 sproc that I have written. The sproc returns the number of rows in a table and is used by the calling process to decide whether or not to update other data.

I have looked at several similar questions on SO but they refer to the use of out parameters instead of using the sproc's return value, for example:

Perl Dbi and stored procedures

I am using a standard DBI connection to the database with both RaiseError and PrintError enabled.

$sql_stmt = "call MY_TABLE_SPACE.MY_SPROC('2011-10-31')";
    $sth = $dbh->prepare($sql_stmt)
         or die "Unable to prepare SQL '$sql_stmt': $rps_met_dbh->errstr";

    $rsp = 0;
    $rsp = $sth->execute();
    unless($rsp) {
        print(STDERR "Unable to execute sproc: $rps_met_dbh->errstr\n");
    }

    print(STDERR "$?\n");

I have tried looking at $h->err for both the statement handle and the db handle.

I would really prefer communicating the number of rows via a return code rather than using SQLSTATE mechanism if I can.

Edit:

I have finished up using a dedicated out parameter to communicate the number of rows updated as follows:

$sql_stmt = "call MY_TABLE_SPACE.MY_SPROC('2011-10-31')";
    $sth = $dbh->prepare($sql_stmt)
         or die "Unable to prepare SQL '$sql_stmt': $rps_met_dbh->errstr";
    $sth = $dbh->bind_param_inout(1, $rows_updated, 128)
         or die "Unable to prepare SQL '$sql_stmt': $rps_met_dbh->errstr";

    $rows_updated = 0;
    $rsp = 0;
    $rsp = $sth->execute();
    unless($rsp) {
        print(STDERR "Unable to execute sproc: $rps_met_dbh->errstr\n");
    }

    print(STDERR "$rows_updated\n");

Edit 2:

And now thinking about this further I have realised that I should apply the PragProg principle of "Tell. Don't Ask." That is, I shouldn't call the sproc. then have it give me back a number before I decide whether or not to call the anopther sproc, ie "Ask".

I should just call the first sproc. and have it decide whether it should call the other sproc or not, ie "Tell" and let it decide.

Answer 1

What is wrong with using an output parameter in your procedure. I've not got a working DB2 lying around right now or I'd provide an example but when I was using it I'm sure you can define output parameters in procedures and bind them with bind_param_inout. I cannot remember if a DB2 procedure can return a value (like a function) but if it can them using "? = call MY_TABLE_SPACE.MY_SPROC('2011-10-31')" would allow you to bind the output return value. If this doesn't work you could use a DB2 function which definitely can return a value. However, at the end of the day the way you get data out of a procedure/function is to bind output parameters - that is just the way it is.

I've no idea what you mean by "using SQLSTATE". I've also no idea what you mean by looking at $h->err as that is only set if the procedure fails or you cannot call the procedure (SQL error etc).