What does the following query find?
(SELECT DISTINCT r.sid
FROM boats b, reserves r
WHERE b.bid = r.bid
AND b.color = 'red')
MINUS
(SELECT DISTINCT r.sid
FROM boats b, reserves r
WHERE b.bid = r.bid
AND b.color = 'green')

Solution (By Examveda Team)

The given SQL query finds the sailor IDs of all sailors who have reserved red boats but not green boats. It does this by first selecting the sailor IDs (r.sid) of reservations where the boat color is 'red' and then subtracting the sailor IDs of reservations where the boat color is 'green'. The MINUS operator is used to find the set difference, and in this context, it retrieves the sailor IDs of sailors who have reserved red boats but not green boats. Option A is the correct choice for describing the query's result.