A Relational Database

Access 2000 is a relational database, which means that data is not stored in a single, very large table. Instead, data is stored in several different tables, all of which are related to one another in such a way that you can join the data from different tables if need be, or retrieve information from several tables at once.

To understand how a relational database works, consider Figure 26-2, which shows what is called a “flat-file database.” A flat-file database, as opposed to a relational database, consists of a single large table, not several different tables. The flat-file database in Figure 26-2 lists the names of contacts. Notice that much of the data stored in the database table is repetitive: The contacts in the database table work for either of two companies, AirTech or DynoAir. Each time you enter information about a person or thing—that is, each time you enter a record—in a flat-file database, you have to enter all the data. In the case of the table in Figure 26-2, you have to enter the name, address, city, state, and ZIP code of either the AirTech company or the DynoAir company.

With a relational database, on the other hand, you wouldn't have to enter the name, address, city, state, and ZIP code of AirTech or DynoAir each time you entered a new contact name in the database table. All you would enter is the contact's last name, first name, and the name of the company that he or she works for. A separate table, also part of the database, would list the addresses of AirTech, DynoAir, and other companies you do business with. If you wanted a complete list like the one in Figure 26-2, you would ask the database for a report that lists contacts, the companies they work for, and the address and phone numbers of those companies.

In a relational database, it is possible to gather information from different tables and assemble that information in one place. In fact, you are encouraged to divide your database into tables. You save time that way, because you don't have to enter repetitive information in many different fields. Instead of entering the same address over and over again, you would enter it only once, in an Addresses table. You also cut down on data-entry errors by saving data in different tables because you don't have to enter the same data over and over.