 | 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, introduced in Hour 7, "Designing Databases," is the process of eliminating duplicate information from a system by splitting information into several tables, each containing a unique value (that is, a primary key). Although data normalization brings many benefits, it means you need to relate an application's tables to each other so that users can view the data in the system as a single entity. After you define relationships between tables, you can build queries, forms, reports, and data access pages that combine information from multiple tables. In this way, you can reap all the benefits of data normalization while ensuring that a system provides users with all the information they need. Referential integrity is another very important topic covered in this hour. Referential integrity consists of a series of rules that the Jet Engine applies to ensure that Jet properly maintains relationships between tables. In this hour you'll learn about the following: |
