FreeTDS Development Group

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

Hi Freddy,

I'm getting somewhere with the dynamic sql with placeholders in
ct-library.
I have some questions, I hope you can help.

Here's how the ct-library API works for dynamic queries

You first prepare the statement. In TDS 5.0 there is a TDS message for
PREPARE.
You can just send the basic SQL string with palceholders, e.g. 
"select * from table where key = ?'

After you have issued the PREPARE, you can call an API to describe for
you the input parameters and the output result set.
This is possible, because in TDS 5.0, Sybase returns you a TDS_PARAMFMT
message and a TDS_RESULT message from the PREPARE directive.

1) What will sp_prepare return you ? I don't suppose it is going to
perform the same service as TDS 5.0....

After prepare, you can set up the parameters for the call using ct_param
or ct_setparam, just like for an RPC call.
You would call these functions once for each parameter.

currently, ct_param and ct_setparam store the parameter information in a
CS_PARAM structure linked list.
There's a root pointer to one of these in the RPC structure. 
I inherited these structures from your work on db-library RPC calls. 
The parameters can be stored by value (ct_param) or reference
(ct_setparam) and the CS_PARAM structure accomodates both types.

The next problem is this incompatibility. 
in the TDSDYNAMIC structure we have a structure for storing parameters,
but it is a TDSPARAMINFO structure. 
I guess I'd like to have a CS_PARAM structure in there as well.

2) how are parameters passed in ODBC ? are they given one by one as in
ct-lib ? does the method support passing parameters by reference ?
    If so, have you some code in ODBC for taking parameters and storing
them in the TDSPARAMINFO structure ?

I will have some more questions I am sure....

Bill 
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