Using the concepts described in the Identifying Existing Relationships section of Chapter 10, and following the steps listed on pages 341342, complete the matrix below and produce the diagrams showing the entity relationships (demonstrated in Figure 10.56) for the matrix. Designate the PKs and FKs in the diagrams. Feel free to make assumptions when carrying out the exercise, and discuss these assumptions in your documentation. You do not need to follow normalization rules or institute business rules (constraints) at this time.

	Physician	Supervisor	Building	Staff	Patient	PatVisits	Treatment	PatReferredBy
Physician
Supervisor
Building
Staff
Patient
PatVisits
Treatment
PatReferredBy

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Here is the specific procedure you'll use to identify the official relationship between a pair of tables in the matrix. (It incorporates the relationship formulas above.) Let's first look at a generic version of the procedure.

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

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

Apply the appropriate formula to the two entries and identify the official relationship between the tables.

Diagram the relationship in the appropriate manner.

Cross out both entries on the matrix.

Now, let's take a look at how you apply this procedure to a pair of tables in the matrix. (In this example, you're working down the left-hand side of the matrix.)

Assume you've selected the BUILDINGS and CLASSES tables. You note that the entry at the junction between BUILDINGS and CLASSES is 1:N.

Now you proceed down the left-hand side of the matrix until you locate the CLASSES table and then note that the entry at the junction between the CLASSES and BUILDINGS table is 1:1.

Using these entries with the appropriate formula, you determine that the official relationship between the BUILDINGS and CLASSES tables is 1:N. (1:N + 1:1 = 1:N)

You create a one-to-many relationship diagram for the BUILDINGS and CLASSES tables.

You cross out the entries on the matrix.

Figure 10.29 shows the results of your work.

Figure 10.29. Identifying the official relationship between the BUILDINGS and CLASSES tables.

Note that the relationship diagram is built from the perspective of the BUILDINGS table. This is due to the fact that the BUILDINGS table is on the one side of the relationship. When you create a simple diagram such as this, I recommend that you always show the one side of the relationship on the left and the many side on the right. Following this practice will make your diagrams easy to read and help ensure that you create them in a consistent manner. (This practice is unnecessary, however, when you create a complex diagram showing the relationships between several tables.)