Using ADO with SQL Native Client

In order to take advantage of new features introduced with SQL Server 2005 such as multiple active result sets (MARS), query notifications, user-defined types (UDTs), or the new xml data type, existing applications that use ActiveX Data Objects (ADO) should use the SQL Native Client OLE DB provider as their data access provider.

If you do not need to use any of the new features of SQL Server 2005, there is no need to use the SQL Native Client OLE DB provider; you can continue using your current data access provider, which is typically SQLOLEDB. If you are enhancing an existing application and you need to use the new features of SQL Server 2005, you should use SQL Native Client OLE DB provider.

Hinweis:
If you are developing a new application it is recommended that you consider using ADO.NET and the .NET Framework Data Provider for SQL Server instead of SQL Native Client to access all the new features of SQL Server 2005. For more information about .NET Framework Data Provider for SQL Server, please see the .NET Framework SDK documentation for ADO.NET.

To enable ADO to use SQL Server 2005 features, some enhancements have been made to the SQL Native Client OLE DB provider which extends the core features of OLE DB. These enhancements primarily serve to allow ADO applications to use new features provided by SQL Server 2005 and to consume two new SQL Server data types: xml and udt, and to also exploit enhancements to the varchar, nvarchar and varbinary data types. SQL Native Client adds the SSPROP_INIT_DATATYPECOMPATIBILITY initialization property to the DBPROPSET_SQLSERVERDBINIT property set for use by ADO applications so that the new data types are exposed in a way compatible with ADO. In addition, the SQL Native Client OLE DB provider also defines a new connection string keyword named DataTypeCompatibility that is set in the connection string.

Hinweis:

Existing ADO applications can access and update XML, UDT, and large value text and binary field values using the SQLOLEDB provider. The new larger varchar(max), nvarchar(max), and varbinary(max) data types are returned as the ADO types adLongVarChar, adLongVarWChar and adLongVarBinary respectively. XML columns are returned as adLongVarChar, and UDT columns are returned as adVarBinary. However, if you use the SQL Native Client OLE DB provider (SQLNCLI) instead of SQLOLEDB, you need to make sure to set the DataTypeCompatibility keyword to "80" so that the new data types will map correctly to the ADO data types.

Enabling SQL Native Client from ADO

To enable the usage of SQL Native Client, ADO applications will need to implement the following keywords in their connection strings:

• Provider=SQLNCLI
• DataTypeCompatibility=80

For more information about the ADO connections string keywords supported in SQL Native Client, see Using Connection String Keywords with SQL Native Client.

The following is an example of establishing an ADO connection string that is fully enabled to work with SQL Native Client, including the enabling of the MARS feature:

Dim con As New ADODB.Connection

con.ConnectionString = "Provider=SQLNCLI;" _
         & "Server=(local);" _
         & "Database=AdventureWorks;" _ 
         & "Integrated Security=SSPI;" _
         & "DataTypeCompatibility=80;" _
         & "MARS Connection=True;"
con.Open

Examples

The following sections provide examples of how you can use ADO with the SQL Native Client OLE DB provider.

Retrieving XML Column Data

In this example, a recordset is used to retrieve and display the data from an XML column in the SQL Server AdventureWorks sample database.

Dim con As New ADODB.Connection
Dim rst As New ADODB.Recordset
Dim sXMLResult As String

con.ConnectionString = "Provider=SQLNCLI;" _
         & "Server=(local);" _
         & "Database=AdventureWorks;" _ 
         & "Integrated Security=SSPI;" _ 
         & "DataTypeCompatibility=80;"

con.Open

' Get the xml data as a recordset.
Set rst.ActiveConnection = con
rst.Source = "SELECT AdditionalContactInfo FROM Person.Contact " _
   & "WHERE AdditionalContactInfo IS NOT NULL"
rst.Open

' Display the data in the recordset.
While (Not rst.EOF)
   sXMLResult = rst.Fields("AdditionalContactInfo").Value
   Debug.Print (sXMLResult)
   rst.MoveNext
End While

con.Close
Set con = Nothing

Hinweis:
Recordset filtering is not supported with XML columns. If used, an error will be returned.

Retrieving UDT Column Data

In this example, a Command object is used to execute a SQL query that returns a UDT, the UDT data is updated, and then the new data is inserted back into the database. This example assumes that the Point UDT has already been registered in the database.

Dim con As New ADODB.Connection
Dim cmd As New ADODB.Command
Dim rst As New ADODB.Recordset
Dim strOldUDT As String
Dim strNewUDT As String
Dim aryTempUDT() As String
Dim strTempID As String
Dim i As Integer

con.ConnectionString = "Provider=SQLNCLI;" _
         & "Server=(local);" _
         & "Database=AdventureWorks;" _ 
         & "Integrated Security=SSPI;" _
         & "DataTypeCompatibility=80;"

con.Open

' Get the UDT value.
Set cmd.ActiveConnection = con
cmd.CommandText = "SELECT ID, Pnt FROM dbo.Points.ToString()"
Set rst = cmd.Execute
strTempID = rst.Fields(0).Value
strOldUDT = rst.Fields(1).Value

' Do something with the UDT by adding i to each point.
arytempUDT = Split(strOldUDT, ",")
i = 3
strNewUDT = LTrim(Str(Int(aryTempUDT(0)) + i)) + "," + _
   LTrim(Str(Int(aryTempUDT(1)) + i))

' Insert the new value back into the database.
cmd.CommandText = "UPDATE dbo.Points SET Pnt = '" + strNewUDT + _
   "' WHERE ID = '" + strTempID + "'"
cmd.Execute

con.Close
Set con = Nothing

Enabling and Using MARS

In this example, the connection string is constructed to enable MARS through the SQL Native Client OLE DB provider, and then two recordset objects are created to execute using the same connection.

Dim con As New ADODB.Connection

con.ConnectionString = "Provider=SQLNCLI;" _
         & "Server=(local);" _
         & "Database=AdventureWorks;" _ 
         & "Integrated Security=SSPI;" _
         & "DataTypeCompatibility=80;" _
         & "MARS Connection=True;"
con.Open

Dim recordset1 As New ADODB.Recordset
Dim recordset2 As New ADODB.Recordset

Dim recordsaffected As Integer
Set recordset1 =  con.Execute("SELECT * FROM Table1", recordsaffected, adCmdText)
Set recordset2 =  con.Execute("SELECT * FROM Table2", recordsaffected, adCmdText)

con.Close
Set con = Nothing

In prior versions of the OLE DB provider, this code would cause an implicit connection to be created on the second execution because only one active set of results could be opened per a single connection. Because the implicit connection was not pooled in the OLE DB connection pool this would cause additional overhead. With the MARS feature exposed by the SQL Native Client OLE DB provider, you get multiple active results on the one connection.

Siehe auch

Andere Ressourcen

Building Applications with SQL Native Client

Hilfe und Informationen

Informationsquellen für SQL Server 2005