Question

(4 points) Q3. Answer with yes or no. Are the following queries equivalent? Query1: SELECT Distinct S.sname FROM Sailors S, Reserves R WHERE S.sid=R.sid AND R.bid=103 Query2: SELECT S.sname FROM Sailors S WHERE S.sid IN (SELECT R.sid FROM Reserves R WHERE R.bid=103) (4 points) Q4. Answer with yes or no. Are the following queries equivalent? Query1: SELECT S.sname FROM Sailors S, Reserves R WHERE S.sid=R.sid AND R.bid<>103 Query2: SELECT S.sname FROM Sailors S WHERE NOT EXISTS( SELECT * FROM Reserves R WHERE S.sid=R.sid AND R.bid=103) (4 points) Q5. Answer with yes or no. Are the following queries equivalent? Query1: SELECT B.bid, COUNT(*) FROM Boats B, Reserves R WHERE R.bid=B.bid AND B.color='red' GROUP BY B.bid Query2: SELECT B.bid, COUNT(*) FROM Boats B, Reserves R WHERE R.bid=B.bid GROUP BY B.bid HAVING B.color='red'

Answer 1

Q3

Ans:- No

Because query 1 has distinct sname whereas query 2 can have same sname too.

Q4

Ans:- No

Because in first query s.sid = r.sid and r,bid !=103

whereas in the second query not exist condition is applied so s.sid != r.sid and r.bid != 103

Q5

Ans:- Yes

Both queries are the same, just different syntax is used.

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