The following two ER diagrams contain both a cardinality ratio constraint and a participation constraint.

QUESTION:

The following two ER diagrams contain both a cardinality ratio constraint and a participation constraint.

a. In the first ER diagram, is the instance diagram on the right consistent with the ER diagram on the left? Why or why not?

b. In the second ER diagram, is the instance diagram on the right consistent with the ER diagram on the left? Why or why not?

SOLUTION:

a.

In the first ER diagram, the instance diagram on the right is not consistent with the ER diagram on the left. The ER diagram specifies the total participation of VEHICLE in relationship Sales. But then, v3 in the instance diagram does not participate in the relationship.

b.

 

In the second ER diagram, the instance diagram on the right is not consistent with the ER diagram on the left. The ER diagram specifies the total participation of SALESPERSON in relationship Sales. But then, s2 in the instance diagram does not participate in the relationship.

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