Consider the Is_Married_to unary relationship in Figure 8-14C (attached) A . Ass

Question

Consider the Is_Married_to unary relationship in Figure 8-14C (attached)

A. Assume that we want to know the date on which a mariage occured. Augment this E-R Diagram to include a Date_Marriage attribute.

B. Because persons sometimes remarry after the death of a spouse or divorce, redraw this E-R Diagram to show the Whole history of marriages (not just the current marriage) for persons. Show the Date_Married attribute on this diagram.

C. In your answer to Problem and Exercise 18B, is it possible to represent a situation in which the same two people marry each other multiple number of times? Explain.

Explanation / Answer

C) This would depend on the key of the table of database. If the name of the person along with spouse's name is a key then another entry with same values will give error. However this ER diagram says nothing of that sort since persons is not shown as a key. The relation "is married to" can have two entries with same couple names but different date so it can support two people remarrying.

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