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UGC-NET | UGC NET CS 2016 Aug – III | Question 9

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  • Last Updated : 25 Nov, 2022
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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 in 3 tuples: 

P = ARC
1056
1055
2563

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

P = ARC
1056
1055
158Null
2563

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

P = AR = C
105

So, option (D) is correct.


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