FreeTDS Development Group

["Thompson, Bill D (London)" <bill_d_thompson AT ml.com>]

Paul,

Sorry, BOL = SQL Server Books Online

Other documentation can be found at Sybase, eg the dblibrary manual at:

http://sybooks.sybase.com/cng1250e.html


You're right - empty varchar strings generically pose this kind of
problem. But for your purposes, what's the difference between an empty
string and NULL ?

Bill

-----Original Message-----
From: freetds-bounces AT lists.ibiblio.org
[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of Paul Robinson
Sent: 02 August 2005 13:13
To: FreeTDS Development Group
Subject: Re: [freetds] Stored Procedure Output Parameters


Thanks Bill.

BOL?? - I don't know what this is.
Presumably there is some documentation somewhere that you are referring 
to for the dblib API - I've been working on this issue we found (in PHP 
really rather than FreeTDS) and this seemed the simplest way to solve 
it. I'm not familiar with the API that is implemented at all. 
Documentation pointers are always appreciated.

Even if this is the case that wouldn't _necessarily_ give a way of 
determining the difference between and empty VARCHAR string and a NULL 
value - would it?

        Paul

Thompson, Bill D (London) wrote:
> Hi Paul,
> 
> The BOL entry for dbretdata() suggests:
> 
> "To determine whether the data really has a null 
>  value (and retnum is not merely out of range), 
>  check for a return value of 0 from dbretlen."
> 
> we certainly implement dbretlen() which returns the column_cur_size of
> the parameter.
> This could well be zero in the case of a NULL return parameter, but if
> not it could be fixed...
> 
> Bill
> 
> -----Original Message-----
> From: freetds-bounces AT lists.ibiblio.org
> [mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of Paul Robinson
> Sent: 02 August 2005 12:09
> To: freetds AT lists.ibiblio.org
> Subject: [freetds] Stored Procedure Output Parameters
> 
> 
> We've been trying to use PHP 5.0.4 with FreeTDS 0.63 in order to
enable 
> communication with a Windows 2000 Server running MS SQL Server 2000.
> 
> We ran into problems with input and output parameters that I believe 
> I've now solved. In order to do so I have had to change PHP code
(which 
> I will be submitting as a PHP bug shortly) and I've added an extra 
> function to dblib/dblib.c to enable the calling application (PHP in
this
> 
> case) to determine if the output parameter is NULL.
> 
> Diff is as follows:
> 
> 3972a3973,3990
>  > int
>  > dbretisnull(DBPROCESS * dbproc, int retnum)
>  > {
>  >       TDSCOLUMN *colinfo;
>  >       TDSPARAMINFO *param_info;
>  >       TDSSOCKET *tds;
>  >
>  >       dbnumrets(dbproc);
>  >
>  >       tds = (TDSSOCKET *) dbproc->tds_socket;
>  >       param_info = tds->param_info;
>  >       if (!param_info || !param_info->columns || retnum < 1 ||
retnum
> 
>  > param_info->num_cols)
>  >               return NULL;
>  >
>  >       return tds_get_null(param_info->current_row, retnum - 1);
>  > }
>  >
>  >
> 
> I hope you'll either point out a more sensible way that I could have 
> implemented this without having to resort to implementing a new
function
> 
> or you will consider this for inclusion in a future release.
> 
> For information the calling code in PHP (ext/mssql/php_mssql.c) looks 
> like this (in _mssql_get_sp_result inside the loop over the result
> columns):
> 
> is_null = dbretisnull(mssql_ptr->link, i);
> if (is_null) {
>       ZVAL_NULL(bind->zval);
> }
> 
> Thanks,
>       Paul


-- 
Paul Robinson
Systems Manager
Business Collaborator Ltd
WWW: http://www.groupbc.com
_______________________________________________
FreeTDS mailing list
FreeTDS AT lists.ibiblio.org
http://lists.ibiblio.org/mailman/listinfo/freetds
--------------------------------------------------------

If you are not an intended recipient of this e-mail, please notify the 
sender, delete it and do not read, act upon, print, disclose, copy, retain or 
redistribute it. Click here for important additional terms relating to this 
e-mail.     http://www.ml.com/email_terms/
--------------------------------------------------------