FreeTDS Development Group

["Castellano, Nicholas" <Nicholas_Castellano AT acml.com>]

> -----Original Message-----
> From: Garrett Goebel [mailto:garrett AT scriptpro.com] 
> Sent: Thursday, October 30, 2003 11:18 AM
> To: 'FreeTDS Development Group'
> Subject: [freetds] FAQ submission: multiple results for a single query
> 
> 
> Thanks for the "multiple result sets" explanation.
> 
> I felt kind of guilty posting because I hadn't checked the 
> FAQ or dug through the mailing list archives extensively for 
> it. On the other hand, I figured if I'd found a bug in the 
> ODBC implementation I might be forgiven.
> 
> This morning I checked the FAQ... and this isn't in there. 
> Here's an attempt to rephrase your explanation into a FAQ 
> submission with some additional examples. Is this the correct 
> way to make a submission? Please check it for errors, 
> omissions, and feel free to add examples where appropriate. 
> For example at the very bottom I've left <todo>'s for odbc 
> and ct-lib examples of moving to and fetching the next result set.
> 
> 
> How do I work with multiple result sets?
> 
> It depends on what you mean by "multiple result sets". 
> FreeTDS supports SQL statements which return multiple 
> consecutive result sets, but not multiple active result sets.

I think this sentence is confusing two separate issues.  What exactly is a
SQL statement which returns "multiple active result sets"?  I don't know of
any single SQL statement that would do that.  I don't like FAQ answers that
strongly depend on a confused viewpoint for interpretation.

> TDS is a strictly "conversational" protocol. The client 
> initiates a call to the server and the server responds. The 
> client can not initiate additional call-response pairs until 
> it has fully dealt with the server's response. I.e., multiple 
> concurrent conversations on the same database connection are 
> not supported.

This is phrased better but it doesn't really address the question I think
you are asking.  The problem is really that the question "How do I work with
multiple result sets?" is a bad question, since it can mean two different
things to different people.

It would be much better to address the two questions separately:  How do I
work with multiple concurrent result sets on the same database handle?  How
do I work with multiple sequential result sets returned from the execution
of a query?

> Multiple consecutive result sets example:
> 
> o  Perl
> 
>   use DBI;
>   my $dbh = DBI->connect(...);
>   my $sth = $dbh->prepare('select 1 select 2');
>   $sth->execute();
>   do {
>     while (my $data = $sth->fetch) {
>         $sth->execute($data->[0]);
>     }
>   } while ($sth->{odbc_more_results});

The *_more_results stuff is specific to the DBD driver.  If your DBI handle
is backed by a DBD::Sybase object, you would need to use "syb_more_results"
instead.  I don't know of a good database-independent way of doing this.

Cheers,
--nick
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