CREATE TABLE TestTable (
	ID int IDENTITY (1, 1) NOT NULL Primary Key,
	Name char (10) NULL 
) 
GO
					

#define _ATL_STATIC_REGISTRY 
#define _ATL_DEBUG_QI   
#define _ATL_DEBUG_INTERFACES

#include <atldbcli.h>
#include <iostream.h>

#define RETURNHR(hr) if(FAILED((HRESULT)hr)) { AtlTraceErrorRecords((HRESULT)hr); return E_FAIL; }


// The user record.
class CTestNullParamInAccessor 
{
public:
     //Parameter variable.
     CHAR m_InParam[2];
     ULONG m_status;

     // Parameter binding.
     BEGIN_PARAM_MAP(CTestNullParamInAccessor)
  	 SET_PARAM_TYPE(DBPARAMIO_INPUT)
	 COLUMN_ENTRY_STATUS(1,m_InParam,m_status)
     END_PARAM_MAP()
};

class CTestOutputAccessor 
{
public:

    // Data elements.
    CHAR m_Name[10];
    ULONG m_status;

    // Output binding.
    BEGIN_COLUMN_MAP(CTestOutputAccessor)
	COLUMN_ENTRY_STATUS(1,m_Name, m_status)
    END_COLUMN_MAP()
};

int main(void)
{
	HRESULT hr;
	CDataSource connection;
	CSession session;
	CCommand<CAccessor< CTestNullParamInAccessor >,CNoRowset> cmdTest;
	// Connect the database, session, and accessors.
	CoInitialize(NULL);
	CDBPropSet	dbinit(DBPROPSET_DBINIT);
	dbinit.AddProperty(DBPROP_INIT_DATASOURCE, OLESTR("srv"));
	dbinit.AddProperty(DBPROP_AUTH_USERID, OLESTR("user_id"));
	dbinit.AddProperty(DBPROP_AUTH_PASSWORD, OLESTR("password"));
	dbinit.AddProperty(DBPROP_INIT_CATALOG, OLESTR("database_name"));
	dbinit.AddProperty(DBPROP_INIT_MODE, (long) DB_MODE_READWRITE);
	dbinit.AddProperty(DBPROP_AUTH_PERSIST_SENSITIVE_AUTHINFO, false);
	dbinit.AddProperty(DBPROP_INIT_LCID, (long)1033);
	dbinit.AddProperty(DBPROP_INIT_PROMPT, (short)4);
	RETURNHR(hr = connection.Open("SQLOLEDB.1",&dbinit))

	// Create the session.
	RETURNHR(hr = session.Open(connection))

	// Insert a record with a "NULL" value on the "name" field.
        // DBSTATUS_S_ISNULL - the OLE DB provider uses a null value 
        // and proceed to next input parameter if there is one.
	cmdTest.m_status = DBSTATUS_S_ISNULL;

        // Open call executes the insert statement.
	RETURNHR(hr = cmdTest.Open(session, "Insert Into TestTable (Name) Values (?)"))
	cmdTest.Close();

	
	// Retrieve the data.
	CCommand<CAccessor< CTestOutputAccessor > > cmdTest2;
	RETURNHR(hr = cmdTest2.Open(session, "Select Name from TestTable"))
	
	RETURNHR(hr = cmdTest2.MoveFirst())
	cout << "NULL Param Insertion Demo" << endl;
	cout << "=========================\n" << endl;
	long i=1;
	do
	{
	   cout << "(" << i++ << ")";
	   if (cmdTest2.m_status == DBSTATUS_S_OK)
		cout << cmdTest2.m_Name<< endl;
	   else if (cmdTest2.m_status == DBSTATUS_S_ISNULL)
		cout << "NULL" << endl;
	   else
		cout << "ERROR" << endl;
	}while (cmdTest2.MoveNext() == S_OK);
	cmdTest2.Close();
	session.Close( );
	connection.Close();
	return S_OK;
}