Responses to two student

I’m studying for my Software Development class and need an explanation.

Many students indicate that relationships are the hardest part of relational data modeling so let’s practice.

Find a relationship and state how you would read it. Looking at the ER diagram example you posted last week may be an easy way to find one. Do not use any class examples or assignments. Provide a screen shot of the relationship you are interpreting.

First, state how the relationship is read from left to right and then from right to left.

Second, state an instance of that relationship at work. This means thinking about the blueprint you just stated and restating it using specific examples.

Let me provide an example you should have already identified.

In Assignment I, Patient is related to Admission.

Patient Admission Relationship.png

1a. Left-to-Right: A Patient is admitted on zero to many Admissions.

1b. Right-to-Left: An Admission specifies one and only one patient being admitted.

2. Dale is a Patient at Panther Memorial. Dale is admitted on an Admission on January 5th. Dale is also admitted on July 10th when he relapses. Thus, Dale has many Admissions. Dale may not have an admission at all. (Zero to Many min and max)

Each example admission belongs only to Dale as multiple patients cannot be listed on an admission. For instance, Dale and Stephanie cannot share the January 5th admission. If Stephanie was admitted on January 5th it would be recorded as a completely different admission. The January 5th and July 10th admissions must specify that it was Dale as you would not want an admission without knowing who the patient is. (One and only one min and max)