ASA SQL User's Guide
  Designing Your Database
    The design process

Step 1:  Identify entities and relationships

To identify the entities in your design and their relationship to each other

1. Define high-level activities    Identify the general activities for which you will use this database. For example, you may want to keep track of information about employees.

2. Identify entities    For the list of activities, identify the subject areas you need to maintain information about. These subjects will become entities. For example, hire employees , assign to a department , and determine a skill level.

3. Identify relationships    Look at the activities and determine what the relationships will be between the entities. For example, there is a relationship between parts and warehouses. Define two roles to describe each relationship.

4. Break down the activities    You started out with high-level activities. Now, examine these activities more carefully to see if some of them can be broken down into lower-level activities. For example, a high-level activity such as maintain employee information can be broken down into:

   • Add new employees.

   • Change existing employee information.

   • Delete terminated employees.

5. Identify business rules    Look at your business description and see what rules you follow. For example, one business rule might be that a department has one and only one department head. These rules will be built into the structure of the database.