GATE 2013 · session-1
Consider the following relational schema (primary keys: Students.rollno, Courses.courseno, and Registration.(rollno,courseno)):
Students(rollno: integer, sname: string)
Courses(courseno: integer, cname: string)
Registration(rollno: integer, courseno: integer, percent: real)
Which of the following queries are equivalent to this query in English?
“Find the distinct names of all students who score more than 90% in the course numbered 107”
(I) SELECT DISTINCT S.sname
FROM Students as S, Registration as R
WHERE R.rollno=S.rollno AND R.courseno=107 AND R.percent>90
(II) π_sname(σ_(courseno=107 ∧ percent>90)(Registration ⋈ Students))
(III) {T | ∃S∈Students, ∃R∈Registration (S.rollno=R.rollno ∧ R.courseno=107 ∧ R.percent>90 ∧ T.sname=S.sname)}
(IV) {⟨S_N⟩ | ∃S_R ∃R_P (⟨S_R,S_N⟩∈Students ∧ ⟨S_R,107,R_P⟩∈Registration ∧ R_P>90)}