Various namespaces available under ADO.NET is given below:
System.Data : It contains the definition for rows, columns, relations, views, tables, constraints, and databases.
System.Data.SqlClient : It is a collection of classes that are helpful in connecting to a Microsoft SQL Server database such as SqlConnection, SqlCommand, SqlDataAdapter, etc.
System.Data.Odbc: It consists of classes that are required for connecting with most Odbc Drivers. These classes include OdbcConnection, OdbcCommand.
System.Data.OracleClient : It has classes required for connection with an Oracle database, OracleConnection, OracleCommand.
