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Data Source Objects (OLE DB)

SQL Native Client uses the term data source for the set of OLE DB interfaces used to establish a link to a data store, such as SQL Server 2005. Creating an instance of the data source object of the provider is the first task of a SQL Native Client consumer.

Every OLE DB provider declares a class identifier (CLSID) for itself. The CLSID for the SQL Native Client OLE DB provider is the C/C++ GUID CLSID_SQLNCLI. With the CLSID, the consumer uses the OLE CoCreateInstance function to manufacture an instance of the data source object.

SQL Native Client is an in-process server. Instances of SQL Native Client OLE DB provider objects are created using the CLSCTX_INPROC_SERVER macro to indicate the executable context.

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

Every connection made through the SQL Native Client OLE DB provider sets these options automatically:

  • SET ANSI_WARNINGS ON
  • SET ANSI_NULLS ON
  • SET ANSI_PADDING ON
  • SET ANSI_NULL_DFLT_ON ON
  • SET QUOTED_IDENTIFIER ON
  • SET CONCAT_OF_NULL_YIELDS_NULL ON

This example uses the class identifier macro to create a SQL Native Client OLE DB provider data source object and get a reference to its IDBInitialize interface.

IDBInitialize*   pIDBInitialize;
HRESULT          hr;

hr = CoCreateInstance(CLSID_SQLNCLI, NULL, CLSCTX_INPROC_SERVER,
    IID_IDBInitialize, (void**) &pIDBInitialize);

if (SUCCEEDED(hr))
{
    //  Perform necessary processing with the interface.
    pIDBInitialize->Uninitialize();
    pIDBInitialize->Release();
}
else
{
    // Display error from CoCreateInstance.
}

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

The SQL Native Client OLE DB provider makes its first connection to a specified instance of SQL Server 2005 as part of a successful data source initialization. The connection is maintained as long as a reference is maintained on any data source initialization interface, or until the IDBInitialize::Uninitialize method is called.

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