Let R = (A, B) and S = (A, C), and let r(R) and s(S) be relations.
Question:
Let R = (A, B) and S = (A, C), and let r(R) and s(S) be relations. Write an expression in SQL for each of the queries below:
a. {< a > | ∃ b (< a, b >∈ r ∧ b = 17)}
b. {< a, b, c > | < a, b >∈ r ∧ < a, c >∈ s}
c. {< a > | ∃ c (< a, c >∈ s ∧ ∃b1, b2 (< a b1 > ∈ r ∧ < c, b2 > ∈ r ∧ b1 > b2))}
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a a b a b r b 17 select distinct A from r where B 17 b ...View the full answer
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