Programming Microsoft® ADO.NET 2.0 Core Reference, 2nd Edition

A Brief Overview of Relational Data Access

Obviously, ADO.NET did not pioneer relational data access. ADO.NET was predated by other ways of processing data from related tables. Let’s review the most common methods of working with data from related tables and quickly compare them to using the DataRelation object.

Join Queries

Join queries predate all Microsoft data access technologies. They’re a simple, standard way to retrieve data from multiple tables in a single query. The following query retrieves data from the Customers, Orders, and Order Details tables in the Northwind database:

SELECT C.CustomerID, C.CompanyName, C.ContactName, C.Phone, O.OrderID, O.EmployeeID, O.OrderDate, D.ProductID, D.Quantity, D.UnitPrice FROM Customers C, Orders O, [Order ...