Section 20.10. Wrap-Up

20.10. Wrap-Up

This chapter introduced relational databases, SQL, ADO.NET and the IDE's visual programming tools for working with databases. You examined the contents of a simple Books database and learned about the relationships among the tables in the database. You then learned basic SQL to retrieve data from, add new data to, and update data in a database.

We discussed the classes of namespaces System.Data and System.Data.SqlClient that allow programs to connect to a database, then access and manipulate its data. We also explained ADO.NET's disconnected model, which enables a program to store data from a database temporarily in local memory as a DataSet.

The second part of the chapter focused on using the IDE's tools and wizards to access and manipulate data sources like a database in GUI applications. You learned how to add data sources to projects and how to use the IDE's drag-and-drop capabilities to display database tables in applications. We discussed how the IDE hides from you the SQL used to interact with the database. You also learned how to add custom queries to GUI applications so that you can display only those rows of data that meet specific criteria. Finally, you learned how to write data from a data source to an XML file.

In the next chapter, we demonstrate how to build Web applications using Microsoft's ASP.NET technology. We also introduce the concept of a three-tier application, in which an application is divided into three pieces that can reside on the same computer or can be distributed among separate computers across a network such as the Internet. One of these tiersthe information tiertypically stores data in an RDBMS like SQL Server.