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GATE | GATE CS Mock 2018 | Question 36

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Consider the following collection of relation schemes: 
 

professor(profname, deptname)
department(deptname, building)
committee(profname,commname)

Find all the professors who are in exactly (i.e., no more and no less) all those committees that Professor Smith is in. 

 

(A)

R2 <- Πcommname(σprofname = Smith(committee)) 
R3 <- Πcommname(committee) – R2 
(committee / R2) – Πprofname(committee ⋈ R3)
 

(B)

R2 <- Πcommname(Πcommname(committee)) 
R3 <- σprofname = Smith(committee) – R2 
(committee / R2) – Πprofname(committee ⋈ R3)
 

(C)

R2 <- Πcommname(Πprofname(committee)) 
R3 <- Πcommname(committee) – R2 
(committee / R2) – σprofname = Smith(committee ⋈ R3)
 

(D)

None of the above
 


Answer: (A)

Explanation:

Option (C) is correct. 

R2 <- Πcommname(σprofname = Smith(committee)) 
R3 <- Πcommname(committee) – R2 
(committee / R2) – Πprofname(committee ⋈ R3)
 


Quiz of this Question
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Last Updated : 03 Jan, 2018
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