Question

…specifically, the fn_listextendedproperty system function in MSSQL 2005.

I have added an Extended Property to my database object, named ‘schemaVersion’. In my MSVC application, using ADO, I need to determine if that Extended Property exists and, if it does, return the string value out of it.

Here is the T-SQL code that does what I want. How do I write this in C++/ADO, or otherwise get the job done?

select value as schemaVer from fn_listextendedproperty(default, default, default, default, default, default, default) where name=N'schemaVersion' 

Here’s the code I tried at first. It failed with the error listed below the code:

_CommandPtr cmd; cmd.CreateInstance(__uuidof(Command)); cmd->ActiveConnection = cnn;  cmd->PutCommandText('select value '     'from fn_listextendedproperty(default, default, default, default, default, default, default) '     'where name=N'schemaVersion''); VARIANT varCount; cmd->Execute(NULL, NULL, adCmdText); 

…here are the errors I peeled out of the ADO errors collection. The output is from my little utility function which adds the extra text like the thread ID etc, so ignore that.

(Proc:0x1930, Thread:0x8A0) INFO : ===   1 Provider Error Messages : ======================= (Proc:0x1930, Thread:0x8A0) INFO : [  1]   (-2147217900) 'Incorrect syntax near the keyword 'default'.' (Proc:0x1930, Thread:0x8A0) INFO :         (SQLState = '42000') (Proc:0x1930, Thread:0x8A0) INFO :         (Source = 'Microsoft OLE DB Provider for SQL Server') (Proc:0x1930, Thread:0x8A0) INFO :         (NativeError = 156) (Proc:0x1930, Thread:0x8A0) INFO : ========================================================== 

EDIT: Updated the call according to suggestions. Also changed ‘SELECT value AS schemaVer’ to just ‘SELECT value’.

EDIT: Changed the first parameter of Execute() to NULL per suggestion. This fixed my original problem, and I proceeded to the next. 🙂

Answer 1

I still have not figured out how to do this directly. To get on with my life, I wrote a stored procedure which called the function:

set ANSI_NULLS ON set QUOTED_IDENTIFIER ON go   ALTER PROCEDURE [dbo].[mh_getSchemaVersion] @schemaVer VARCHAR(256) OUTPUT AS     select @schemaVer = CAST( (select value from fn_listextendedproperty(default, default, default, default, default, default, default) where name=N'schemaVersion') AS varchar(256) )     return @@ROWCOUNT 

…and then called thst sproc from my ADO/C++ code:

_CommandPtr cmd; cmd.CreateInstance(__uuidof(Command)); cmd->ActiveConnection = cnn; cmd->PutCommandText('mh_getSchemaVersion')_l  _variant_t schemaVar; _ParameterPtr schemaVarParam = cmd->CreateParameter('@schemaVer', adVarChar, adParamOutput, 256); cmd->GetParameters()->Append((IDispatch*)schemaVarParam);  cmd->Execute(NULL, NULL, adCmdStoredProc);  std::string v = (const char*)(_bstr_t)schemaVarParam->GetValue();  ver->hasVersion_ = true; 

…which works, but I didn’t want to have to deploy a new stored procedure.

So if anyone can come up with a solution to the original problem and show me how to call the system function directly from ADO/C++, I will accept that as the answer. Otherwise I’ll just accept this.