Re: Empty VARCHAR parameters converted to NULL

I was looking at this issue. The problem raise when you want a return
value but you want to pass a empty or a NULL varchar. How to
differentiate in this case? value cannot be NULL for return
parameters.

Frediano


2016-01-19 18:25 GMT+00:00 Joshua Lang <[email protected]>:
> I've read that older versions didn't even support passing 0-length data
> (prior to TDS 7.0 I believe). If this could be supported for later versions
> of TDS 7.0, that would be great.
>
> Thanks.
>
> On Tue, Jan 19, 2016 at 2:52 AM, Frediano Ziglio <[email protected]> wrote:
>
>> 2016-01-16 1:41 GMT+00:00 Joshua Lang <[email protected]>:
>> > In the latest version of FreeTDS-dblib (0.95.79) I'm passing rpc VARCHAR
>> > parameters of 0 length, but non-NULL (empty strings). FreeTDS seems to
>> turn
>> > these into NULL values before passing them on to SQL Server. From what
>> I've
>> > read, it seems as if older databases didn't support passing empty
>> strings,
>> > but newer ones do? (i.e. TDS 7.0+ do support empty strings).
>> >
>> > It seems as this is a known issue, but I was wondering if it is possible
>> to
>> > fix it for the newer versions of SQL server? E.g. in dbrpcparam()
>> passing a
>> > non-NULL pointer to the 'value' parameter and a 0 to 'datalen' would
>> > indicate an empty string is desired if possible.
>> >
>> > Thoughts?
>>
>>
>> The main problem is not libTDS (the code library) but dbrpcparam
>> specification.
>> datalen < 0 is invalid for variable fields (like VARCHAR) and 0 is used
>> for NULL
>> value (no matter the data pointer). But looks like your suggestion
>> (not NULL value
>> and 0 datalen) could be a good choice.
>> Not sure however if this could work with all types and server versions
>> (for instance
>> 0 size TEXT).
>> We can do it but I'm not thinking about backporting it to 0.95.
>>
>> Frediano
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