MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 4: Rowsets

Rowset Creation Example

The code in this example shows how to create a rowset.

/////////////////////////////////////////////////////////////////
// myCreateRowset
//
// This function creates an OLE DB rowset object from the given
// provider's session object. It first obtains a default table
// name from the user through the tables schema rowset, if
// supported, and then creates a rowset object by one of two methods:
//
// - If the user requested that the rowset object be created
//    from a command object, it creates a command object and then
//    obtains command text from the user, sets properties and
//    the command text, and finally executes the command to
//    create the rowset object.
// - Otherwise, the function obtains a table name from the user
//    and calls IOpenRowset::OpenRowset to create a rowset object
//    over that table that supports the requested properties.
//
/////////////////////////////////////////////////////////////////
HRESULT   myCreateRowset
   (
   IUnknown *           pUnkSession,
   IUnknown **          ppUnkRowset
   )
{
   HRESULT              hr;
   IUnknown *           pUnkCommand                      = NULL;
   IOpenRowset *        pIOpenRowset                     = NULL;
   WCHAR                wszTableName[MAX_NAME_LEN + 1]   = {0};

   const ULONG          cProperties                      = 2;
   DBPROP               rgProperties[cProperties];
   DBPROPSET            rgPropSets[1];

   // Obtain a default table name from the user by displaying the
   // tables schema rowset if schema rowsets are supported.
   CHECK_HR(hr = myCreateSchemaRowset(DBSCHEMA_TABLES, pUnkSession, 
            MAX_NAME_LEN, wszTableName));

   // Set properties on the rowset, to request additional functionality.
   myAddRowsetProperties(rgPropSets, cProperties, rgProperties);

   // If the user requested that the rowset be created from a
   // command object, create a command, set its properties and
   // text, and execute it to create the rowset object.
   if( g_dwFlags & USE_COMMAND )
   {
      WCHAR      wszCommandText[MAX_NAME_LEN + 1];

      // Attempt to create the command object from the provider's
      // xession object. Note that commands are not supported by
      // all providers, and this will fail in that case.
      CHECK_HR(hr = myCreateCommand(pUnkSession, &pUnkCommand));
      
      // Get the command text that we will execute from the user.
      if( !myGetInputFromUser(wszCommandText, L"\nType the command "
         L"to execute [Enter = `select * from %s`]: ", wszTableName) )
      {
         swprintf(wszCommandText, L"select * from %s", wszTableName);
      }

      // And execute the command the user entered.
      CHECK_HR(hr = myExecuteCommand(pUnkCommand, wszCommandText,
               1, rgPropSets, ppUnkRowset));
   }
   // Otherwise, the user gets the default behavior, which is to use
   // IOpenRowset to create the rowset object from the session object.
   // IOpenRowset is supported by all providers; it takes a TableID
   // and creates a rowset containing all rows in that table. It is
   // similar to using SQL command text of "SELECT * FROM TableID".
   else
   {
      DBID         TableID;

      // Create the TableID.
      TableID.eKind            = DBKIND_NAME;
      TableID.uName.pwszName   = wszTableName;

      // Obtain the table name from the user.
      myGetInputFromUser(wszTableName, L"\nType the name of the table "
         L"to use [Enter = `%s`]: ", wszTableName);

      // Get the IOpenRowset interface, and create a rowset object
      // over the requested table through OpenRowset.
      XCHECK_HR(hr = pUnkSession->QueryInterface(
                IID_IOpenRowset, (void**)&pIOpenRowset));
      XCHECK_HR(hr = pIOpenRowset->OpenRowset(
                NULL,            // pUnkOuter
                &TableID,        // pTableID
                NULL,            // pIndexID
                IID_IRowset,     // riid
                1,               // cPropSets
                rgPropSets,      // rgPropSets
                ppUnkRowset));   // ppRowset
   }

CLEANUP:
   if( pIOpenRowset )
      pIOpenRowset->Release();
   if( pUnkCommand )
      pUnkCommand->Release();
   return hr;
}