p.189b

"Find the names of sailors who have reserved both a red and a green boat."

SELECT S.sname

FROM Sailors S, Boats B1, Reserves R1, Boats B2, Reserves R2

WHERE S.sid = R1.sid AND R1.bid = B1.bid

AND S.sid = R2.sid AND R2.bid = B2.bid

AND (B1.color = 'red' AND B2.color = 'green')

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