You could certainly modify your table design further. But at some point you need to start considering performance. Performance can be adversely impacted if, on a regular basis, you need to join multiple tables with a lot of data. We recommend that you keep the number of tables in your database to a minimum while following the normalization rules as closely as possible. You will soon learn that database design is as much art as it is science.

Security Considerations

Probably the most overlooked aspect of database design is security, when it should be a major consideration. By not securing your database and thereby your data, you are asking for trouble. Not all data is intended for everyone’s eyes, and not everyone should have the ability to manipulate your data and definitely not your database’s structure. The majority of your database users will only need and should only be granted read (or select) access. When designing your database, you should establish a list of policies and users for your database. A database user is anyone who needs access to any part of your database. The highest level of user is the database administrator who will have access to all database objects and data. Other users will only have access to certain objects and data. The average end user will only have access to certain objects, but should never have the ability to alter your database structure. It never ceases to amaze us how many organizations have one “global” user that has complete control of the database. This is typically a bad scenario, not because people are intentionally malicious, but because they are people and no one is perfect. The impact of a simple mistake can take hours and even days to reverse, if reversal is possible at all. Policies are basically rules that define which actions a user can perform on your database. Most RDMSs enable you to assign a separate set of policies, or rights, for each object in your database. User rights generally fall into one of six different categories:

SELECT enables the user to view data.

INSERT enables the user to create new data.

UPDATE enables the user to modify existing data.

DELETE enables the user to delete data.

EXECUTE enables the user to execute a stored procedure.

ALTER enables the user to alter database structure.

We will discuss stored procedures in Session 4, “Building a Database.”

Note

Each user in a database should have a unique user name and password combination. This will enable your RDMS to enforce the security policies you have established for the user.

S E S S I O N

4

Building a Database

Session Checklist

Building a database using SQL Server

Using database objects

In the previous session, we explained how to design and build a database. In this session, you’ll build the Music database using SQL Server. (If you’re going to build the database as you go through this session, use either SQL Server 7.0 or 2000.)

When working with SQL Server, you can create a database and its related objects in one of two ways. Probably the easiest method is to use Enterprise Manager. Enterprise Manager

provides a user interface that enables you to graphically create a database, tables, constraints, and so on. If you installed SQL Server on your local machine, Enterprise Manager should be located in the SQL Server program group on the Start menu.

The second method of creating a database with SQL Server is to execute Transact-SQL (T-SQL) commands against your SQL Server. Although writing T-SQL commands is a little more difficult than using Enterprise Manager, you have greater control of the objects you create and can save time.

Which method you use is a matter of personal preference. Throughout this session, we demonstrate creating database objects with both methods.

Creating a Database

The first step in building a database with SQL Server is to actually create the database. That’s right. SQL Server is a piece of software that runs on a computer, or server. Once the SQL Server software is installed you can create a database (or databases) with the SQL Server software

that is then managed by that SQL Server software. Many people refer to SQL Server as a database, which it is, sort of. SQL Server is actually an application, a Relational Database Management System (RDBMS), which can contain multiple databases.

We will be using SQL Server 7.0 to create the database in this session. If you are using SQL Server 2000, the steps will be slightly different.

Note

OK, let’s create the Music database. You’ll start by creating the database using Enterprise Manager and perform the following steps:

1.Expand the SQL Server Group item, if it isn’t already expanded, in the Enterprise Manager tree. Once expanded you should see a list of SQL Servers that are registered with Enterprise Manager.

2.Right-click the SQL Server in which you want to create the Music database.

3.Select New Database. Figure 4-1 illustrates steps 1, 2, and 3.

4.You see the Database Properties dialog box, shown in Figure 4-1. On the General tab, enter Music in the Name field. The Database Properties dialog box allows you to control other features of your database such as file growth, maximum database size, transaction log files, and so on. For the sake of brevity, accept the defaults.

Figure 4-1 Specifying database properties with Enterprise Manager

That’s it. You have created a SQL Server database using Enterprise Manager. If you want to create a database with T-SQL, follow these steps:

1.Select Start Programs Microsoft SQL Server Query Analyzer to open SQL Server’s Query Analyzer.

2.You see the Connect to SQL Server dialog box. Select the SQL Server on which you would like to create the Music database from the SQL Server drop-down box. Select the Use SQL Server authentication radio button. Now enter the appropriate authentication information in the Login Name and Password fields as shown in Figure 4-2.

Figure 4-2 Query Analyzer logon

3.In the Query Analyzer window, enter the following T-SQL statement:

USE master GO

CREATE DATABASE Music ON PRIMARY ( NAME = MusicData,

FILENAME = ‘C:\MSSQL7\data\MusicData.mdf’

)

In the previous script, you may need to alter the FILENAME string so that it reflects a valid path on your computer.

Note

In step 3, you essentially created a database named Music and specified that the data should be stored in the MusicData.mdf file located, in this example, in the C:\MSSQL7\data directory. The CREATE DATABASE statement accepts many other parameters, such as MAXSIZE, FILEGROWTH, SIZE, and so on. However, again, for the sake of brevity, you used the SQL Server defaults.

Once you have entered the previous SQL statement in the Query Analyzer window, hit the F5 button, which will execute the SQL script.

Note