Chapter 4: Understanding Table Relationships


Understanding bulletproof database design

Normalizing database data

Looking at common table relationships

Understanding integrity rules

Adding key fields to tables

We've already covered one of the most basic assumptions about relational database systems — that is, that data is spread across a number of tables that are related through primary and foreign keys. 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 exists 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 becomes more complex, you may need to add more tables to the design. For example, a database to manage employee affairs for a company will include tables for employee information (name, Social Security number, address, hire date, and so on), payroll information, benefits programs the employee belongs to, and so on.

This chapter uses a variety of data from different business ...

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