Database Design for Mere Mortals™: A Hands-On Guide to Relational Database Design, Second Edition

Identifying Relationships

Use this procedure to identify the official relationship between a pair of tables within a table matrix:

1. Select a pair of tables and note the entry at the junction of the first table and the second table.

2. Locate the second table on the same side of the matrix you're working on and note the entry and the junction between it and the first table on the opposite side of the matrix.

3. Apply the appropriate formula (shown below) to the two entries and identify the official relationship between the tables.

   a. 1:1 + 1:1 = 1:1

   b. 1:N + 1:1 = 1:N

   c. 1:N + 1:N = M:N

4. Diagram the relationship in the appropriate manner.

5. Cross out both entries on the matrix.