# DBMS Grand Test 1 Question51

+1 vote

Consider the folowing entity relation diagram

Below are three possible relationships set for this entity relation diagram

1
A B C D
a1 b1 c1 d1
a1 b1 c1 d2
2
A B C D
a1 b1 c1 d1
a1 b1 c2 d2
3
A B C D
a1 b1 c1 d1
a1 b2 c1 d1

Assume that different symbols stand for different values. which of the above could not be the relationship set for the entity relation diagram ?

(A) 1 only

(B) 1 and 2 only

(C) 2 only

(D) 1, 2 and 3 only

asked Sep 10, 2016 in DBMS
reshown Dec 24, 2018

Relation 2 should also be invalid since there exist many to one relationships between A and C and B and C whereas according to table 2 it is showing one to many relationship which is inconsistent with the given er diagram. Hence B should be the correct option.
answered Sep 19, 2016 by (1,860 points)
+1 vote

when a relationship's degree is more than binary (ternary and 4-ary....) and there is more than one arraw then in literature it is interpreted in two ways.

1st interpretation:

Since C has arrow it is interpreted as

for every ABD there is atmost one C  [ ABD $\dpi{120} \bg_white \rightarrow$ C]

Since D has arrow it is interpreted as

for every ABC there is atmost one D  [ABC$\dpi{120} \bg_white \rightarrow$ D]

2nd interpretation:

Since C, D have arrows, in this interpretation it is interpreted as A$\dpi{120} \bg_white \rightarrow$C and A$\dpi{120} \bg_white \rightarrow$D and B$\dpi{120} \bg_white \rightarrow$C, B$\dpi{120} \bg_white \rightarrow$D

Since there are two interpretations if you follow first interpretation then Answer is (A) and if you follow 2nd interpretation then it is (B).

Note: Marks are given for A and B

answered Sep 20, 2016 by (36,850 points)