Data Source Objects

OLE DB uses the term data source for the set of OLE DB interfaces used to establish a link to a data store, such as Microsoft SQL Server. Creating an instance of the data source object of the provider is the first task of an OLE DB consumer.

Every OLE DB provider declares a class identifier for itself. The class identifier for SQLOLEDB is the C/C++ macro CLSID_SQLOLEDB. With the class identifier, the consumer uses the OLE CoCreateInstance function to manufacture an instance of the data source object.

SQLOLEDB is an in-process server. Instances of SQLOLEDB objects are created using the CLSCTX_INPROC_SERVER macro to indicate the executable context.

The SQLOLEDB data source object exposes the OLE DB initialization interfaces that allow the consumer to connect to existing SQL Server databases.

Example

This example uses the class identifier macro to create a SQLOLEDB data source object and get a reference to its IDBInitialize interface.

IDBInitialize* pIDBInitialize;
HRESULT    hr;
  
hr = CoCreateInstance(CLSID_SQLOLEDB, NULL, CLSCTX_INPROC_SERVER,
  IID_IDBInitialize, (void**) &pIDBInitialize);
  
if (SUCCEEDED(hr))
{
  //  Do stuff with the interface.
  pIDBInitialize->Uninitialize();
  pIDBInitialize->Release();
}
else
{
  // Display error from CoCreateInstance.
}
  

With successful creation of an instance of a SQLOLEDB data source object, the consumer application can continue on by initializing the data source and creating sessions. OLE DB sessions present the interfaces that allow data access and manipulation.

SQLOLEDB makes its first connection to a specified SQL Server as part of successful data source initialization. The connection is maintained as long as a reference is maintained on any data source initialization interface, or until IDBInitialize::Uninitialize is called.