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UGC-NET | UGC NET CS 2016 Aug – III | Question 9
  • Last Updated : 16 Apr, 2018

Suppose database table T1(P, R) currently has tuples {(10, 5), (15, 8), (25, 6)} and table T2 (A, C) currently has {(10, 6), (25, 3), (10, 5)}. Consider the following three relational algebra queries RA1, RA2 and RA3:
RA1 : T1T1.P = T2.A T2 where ⨝is natural join symbol
RA2 : T1T1.P = T2.A T2 where ⟕ is left outer join symbol
RA3 : T1T1.P = T2.A and T1.R = T2.CT2
The number of tuples in the resulting table of RA1, RA2 and RA3 are given by:
(A) 2, 4, 2 respectively
(B) 2, 3, 2 respectively
(C) 3, 3, 1 respectively
(D) 3, 4, 1 respectively


Answer: (D)

Explanation: RA1 : T1T1.P = T2.A T2 where ⨝is natural join symbol. It will result 3 tuples:



P = A R C
10 5 6
10 5 5
25 6 3



RA2 : T1T1.P = T2.A T2 where ⟕ is left outer join symbol. It will rewult in 4 tuples.



P = A R C
10 5 6
10 5 5
15 8 Null
25 6 3



RA3 : T1T1.P = T2.A and T1.R = T2.CT2. It will result in 1 tuple.


P = A R = C
10 5



So, option (D) is correct.

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