SQL Basics in ADO.NET

When you interact with a data source through ADO.NET, you use SQL to retrieve, modify, and update information. In some cases, ADO.NET will hide some of the details for you or even generate required SQL statements automatically. However, to design an efficient database application with a minimal amount of frustration, you need to understand the basic concepts of SQL.
SQL (Structured Query Language) is a standard data access language used to interact with relational databases. Different databases differ in their support of SQL or add other features, but the core commands used to select, add, and modify data are common. In a database product such as SQL Server, it’s possible to use SQL to create fairly sophisticated SQL scripts for stored procedures and triggers (although they have little of the power of a full object-oriented programming language). When working with ADO.NET, however, you’ll probably use only the following standard types of SQL statements:
• A Select statement retrieves records.
• An Update statement modifies existing records.
• An Insert statement adds a new record.
• A Delete statement deletes existing records.
If you already have a good understanding of SQL, you can skip the next few sections.
Otherwise, read on for a quick tour of SQL fundamentals. nTip To learn more about SQL, use one of the SQL tutorials available on the Internet, such as the one at http://www.w3schools.com/sql. If you’re working with SQL Server, you can use its thorough Books
Online help to become a database guru.

Browsing and Modifying Databases in Visual Studio

As an ASP.NET developer, you may have the responsibility of creating the database required for a web application. Alternatively, it may already exist, or it may be the responsibility of a dedicated database administrator. If you’re using a full version of SQL Server, you’ll probably use a graphical tool such as SQL Server Management Studio to create and manage your databases.

If you don’t have a suitable tool for managing your database, or you don’t want to leave the comfort of Visual Studio, you can perform many of the same tasks using Visual Studio’s
Server Explorer window.
Here’s how you can get started. First, choose View äServer Explorer from the Visual Studio menu to show the Server Explorer window. Then, using the Data Connections node in the
Server Explorer, you can connect to existing databases or create new ones. Assuming you’ve installed the pubs database (see the readme.txt file for instructions), you can create a connection to it by following these steps:
1. Right-click the Data Connections node, and choose Add Connection. If the Choose
Data Source window appears, select Microsoft SQL Server and then click Continue.
2. If you’re using a full version of SQL Server, enter localhost as your server name. This indicates the database server is the default instance on the local computer. (Replace this with the name of a remote computer if needed.) If you’re using SQL Server Express, you’ll need to use the server name localhost\SQLEXPRESS instead, as shown in
Figure 15-2. The SQLEXPRESS part indicates that you’re connecting to a named instance of SQL Server. By default, this is the way that SQL Server Express configures itself when you first install it.
3. Click Test Connection to verify that this is the location of your database. If you haven’t installed a database product yet, this step will fail. Otherwise, you’ll know that your database server is installed and running.
4. In the Select or Enter a Database Name list, choose the pubs database. (In order for this to work, the pubs database must already be installed. You can install it using the database script that’s included with the sample code, as explained in the following section.)
If you want to see more than one database in Visual Studio, you’ll need to add more than one data connection.