Consider the Is_Married_to unary relationship in Figure 8-14C (attached) A . Ass
ID: 3533501 • Letter: C
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.