IN THIS CHAPTER
Understanding relational database theory
Normalizing database data
Identifying data anomalies from unnormalized data
Looking at common table relationships
Understanding primary and foreign keys
Establishing a primary key
Viewing relationships in an Access database
Creating table relationships
Choosing a join type for table relationships
Knowing the rules of referential integrity
Enforcing referential integrity in Access databases
We've already looked at one of the most basic assumptions about relational database systems — that is, that data are spread across a number of tables that are related through primary and foreign keys (see Chapter 1 for a review). Although this basic principle is easy to understand, it can be much more difficult to understand why and when data should be broken into separate tables.
Because the data managed by a relational database such as Access exist in a number of different tables, there must be some way to connect the data. The more efficiently the database performs these connections, the better and more flexible the database application as a whole will function.
Although databases are meant to model real-world situations or at least manage the data involved in real-world situations, even the most complex situation is reduced to a number of relationships between pairs of tables. As the data managed by the database become more complex, you may need to add more tables to the design. For instance, a database to ...