Hey guys can you tell me what are the different namespaces used in the project to connect the database?

Yes sure , the namespaces use to connect database are
1. System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.
2. System.Data.SqlClient – classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
3. System.Data.Odbc – classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.
4. System.Data.OracleClient – classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.