Question

Suppose we have the following relations Sailors (sid, sname, age) Boats (bid, bname, color) Reserves (sid, bid, date) Note: the primary key fields are underlined. Please complete the following query by using relational algebra

Answer 1

Question 7: For this subquery is used in the where clause to max age in the sailors table, then the sailor name with that age is extracted.

SELECT sname

FROM Sailors

WHERE age = (SELECT MAX(age) FROM Sailors);

Question 8: The join between the table Sailors and Reserves is applied along with subquery in the where clause to get the first reserved date.

SELECT s.sname

FROM Sailors AS s

INNER JOIN Reserves AS r

ON s.sid = r.sid

WHERE r.date = (SELECT MIN(date) FROM Reserves);