Multiple choice

Consider the set of relations shown below and the SQL query that follows. Students: (Roll_number, Name, Date_of_birth) Courses: (Course number, Course_name, Instructor) Grades: (Roll_number, Course_number, Grade) select distinct Name from Students, Courses, Grades where Students. Roll_number = Grades.Roll_number and Courses.Instructor = Korth and Courses.Course_number = Grades.Course_number and Grades.grade = A Which of the following sets is computed by the above query?

  1. Names of students who have got an A grade in all the courses taught by Korth.

  2. Names of students who have got an A grade in all the courses.

  3. Names of students who have got an A grade in at least one of the courses taught by Korth.

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Names are unique since they are selected distinct, so one person will be selected only once, even when he has got grade A in any number of courses taught by Korth. So, if a name is appearing it is not necessary that he scored grade A in all the courses, but scored grade A in at least one course.

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