Practical Examples: Establishing the Relationships Between the Tables Included in the Time and Billing Database

Why This Chapter Is Important

A relationship exists between two tables when one or more key fields from one table are matched to one or more key fields in another table. The fields in both tables usually have the same name, data type, and size. Relationships are a necessary by-product of the data normalization process. Data normalization, which was introduced in Chapter 1, "Access as a Development Tool," and is covered in additional detail in this chapter, is the process of eliminating duplicate information from your system by splitting information into several tables, each containing a unique value (primary key). Although data normalization brings many benefits, you need to relate your application's tables to each other so that your users can view the data in the system as a single entity. After you define relationships between tables, you can build queries, forms, and reports that combine information from multiple tables. In this way, you can reap all the benefits of data normalization while ensuring that your system provides users with all the information they need.