Tài liệu Utilizing Properties for Tables and Columns doc

Utilizing Properties for Tables and Columns
Tables and columns, like other objects in your database, have properties that allow you to
control the data that is going into your tables. For example, in the Customers table, you
can see the properties for the first column, called CustomerID. The extent to which you
use the properties depends on what your needs are.
At the table level, you also have properties that you can utilize that help you create and
enforce business rules, which are discussed later in this chapter.
You will create your tables by breaking down your data into logical entities. When you
do so, you need to keep in mind how you break them down, and you need to break them
down so that they are created in what is called normalization.
SQL Server has come a long way over the years. For every version, Microsoft works hard
not only to make SQL Server more powerful, but also easier to work with. This includes
tools that come with the product and from other applications. Visual Studio .NET is a
good example of tools for working with SQL Server from another product.
If you are not familiar with databases, here's a quick overview. Databases allow you to
work with data in a manner that reflects the real world on the computer. You can take a
real subject, such as Customers, and store that information in tables. A file cabinet is
analogous to a database. Within the file cabinet you may have your client folders. Other
folders might contain information on Orders or Invoices. One of these folders could be
compared to a table of customers. Within the Customers folder, you might have
individual pages of information on a customer. Each page that you have on an individual
customer would be a row, or a record within a table. On each page, you would have
pieces of information such as Customer Name, Address, Phone, and so on. These would
be fields, or columns, within each row.
In a database, you will also have objects that allow you to query information within tables
and update information. In SQL Server, you will use Views, Stored Procedures, and
Functions to view and update data within the database. To use these objects, you need to
be able to create them. To create a database along with its tables in SQL Server, you can
use code or tools that came with SQL, such as the Enterprise Manager, if you have
installed one of the versions that include these tools.
Fortunately, you can use tools that are built within Visual Studio .NET to create and

modify your databases. The primary tool you will use is called the Server Explorer, as
shown in Figure 2.1.
Figure 2.1. From the Server Explorer within Visual Studio .NET, you can perform
most of the tasks that are necessary to maintain a database.