1) .NET Framework Data Provider for SQL Server – Provides access to Microsoft SQL Server 7.0 or later version. It uses the System.Data.SqlClient namespace.2) .NET Framework Data Provider for OLE DB – Provides access to databases exposed by using OLE DB. It uses the System.Data.OleDb namespace.3) .NET Framework Data Provider for ODBC – Provides access to databases exposed by using ODBC. It uses the System.Data.Odbc namespace.4) .NET Framework Data Provider for Oracle – Provides access to Oracle database 8.1.7 or later versions. It uses the System.Data.OracleClient namespace.