Consider the following Relational Schema:Sailors (sid: integer, sname: string, rating: integer, age: real)Boats (bid: integer, bname: string, color: string)Reserves (sid: integer, bid: integer, day: date)Consider the Following Statements:S1:SELECT S.snameFROM Sailors SWHERE NOT EXISTS (SELECT *FROM Sailors S2WHERE S2.age S2: SELECT S.snameFROM Sailors SWHERE S.rating ANY (SELECT S2.ratingFROM Sailors S2WHERE S2.age Which of the following is true regarding S1 and S2?a)Both will compute the same result.b)S1 will result in the names of sailors whose rating is more than some sailor whose age is less than 21.c)They will generate different outputs.d)None of these.Correct answer is option 'C'. Can you explain this answer?

Question

Consider the following Relational Schema:Sailors (sid: integer, sname: string, rating: integer, age: real)Boats (bid: integer, bname: string, color: string)Reserves (sid: integer, bid: integer, day: date)Consider the Following Statements:S1:SELECT S.snameFROM Sailors SWHERE NOT EXISTS (SELECT *FROM Sailors S2WHERE S2.age S2: SELECT S.snameFROM Sailors SWHERE S.rating > ANY (SELECT S2.ratingFROM Sailors S2WHERE S2.age Which of the following is true regarding S1 and S2?a)Both will compute the same result.b)S1 will result in the names of sailors whose rating is more than some sailor whose age is less than 21.c)They will generate different outputs.d)None of these.Correct answer is option 'C'. Can you explain this answer?

Answer

Explanation:
The given statements S1 and S2 are two different SQL queries operating on the same relational schema. Let's analyze each query separately and then compare the outputs.

S1: SELECT S.sname FROM Sailors S WHERE NOT EXISTS (SELECT * FROM Sailors S2 WHERE S2.age < />

This query selects the names of sailors from the Sailors table where there does not exist any sailor in the Sailors table whose age is less than 21. In other words, it selects the names of sailors who are all at least 21 years old.

S2: SELECT S.sname FROM Sailors S WHERE S.rating > ANY (SELECT S2.rating FROM Sailors S2 WHERE S2.age < />

This query selects the names of sailors from the Sailors table where their rating is greater than the rating of at least one sailor in the Sailors table whose age is less than 21. In other words, it selects the names of sailors whose rating is higher than the rating of some sailor who is less than 21 years old.

Comparison:
Now let's compare the outputs of both queries:

- If there exists at least one sailor whose age is less than 21, then the subquery in S2 will return a non-empty result set, and hence S2 will select some sailors' names whose rating is higher than the rating of that sailor. On the other hand, the subquery in S1 will return an empty result set, because it checks if there exists any sailor whose age is less than 21, and the answer is no. Therefore, the outputs of S1 and S2 will be different.

- However, if there are no sailors in the Sailors table whose age is less than 21, then both the subqueries in S1 and S2 will return empty result sets. In this case, the outputs of S1 and S2 will be the same, as both queries will not select any names.

Conclusion:
Based on the above analysis, it can be concluded that the outputs of S1 and S2 will be different in general. Therefore, option C is the correct answer.

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