Question

I am in a database class currently and am stuck on number 3 on this problem.

Problem 2 A university database has the following relations:

STUDENTS (Sno: int, Sname: varchar(64), Gender: ‘F’ or ‘M’, Age: int),
COURSES (Cno: int, Cname: varchar(32)),
ENROLLMENT (Sno: int, Cno:int, Grade: int).

Write SQL statements to perform the following tasks:

1. Find the names of the youngest students.
2. Find the Sno for students who enroll at least in courses with Cno = 1 and Cno = 3.
3. Find the names of the students who enroll in all the courses.
4. Find the names of the students who enroll more than 3 courses.
5. Find the name and the average grade for each course.
6. Find the names of students whose grades in the course “DBMS” is above the average grade.

Answer 1

3

SELECT S.Sname
FROM Students AS S INNER JOIN Enrollment AS E ON S.Sno = E.Sno
GROUP BY S.Sno, S.Sname 
HAVING COUNT(*) = (SELECT COUNT(*) FROM Courses)

4

SELECT S.Sname
FROM Students AS S INNER JOIN Enrollment AS E ON E.Sno = S.Sno
GROUP BY S.Sno, S.Sname
HAVING COUNT(*) > 3

5

SELECT C.CName, AVG(E.Grade) AS AvgGrade
FROM Courses AS C INNER JOIN Enrollment AS E ON C.CNo = E.CNo 
GROUP BY C.Cno, C.CName