SQL

Students (rollno: integer, name: string, age: integer, cgpa: real)
Courses (courseno: integer, cname: string, credits: integer)
Enrolled (rollno: integer, courseno: integer, grade: string)

One or more correct

• A

  SELECT S.name
  FROM Students S
  WHERE EXISTS (SELECT * FROM Enrolled E
                WHERE E.courseno = 1470
                      AND E.rollno = S.rollno);

• B

  SELECT S.name
  FROM Students S
  WHERE SIZEOF (SELECT * FROM Enrolled E
                WHERE E.courseno = 1470
                      AND E.rollno = S.rollno) > 0;

• C

  SELECT S.name
  FROM Students S
  WHERE 0 < (SELECT COUNT(*)
             FROM Enrolled E
             WHERE E.courseno = 1470
                   AND E.rollno = S.rollno);

• D

  SELECT S.name
  FROM Students S NATURAL JOIN Enrolled E
  WHERE E.courseno = 1470;