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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