Consider the following relational schema: Students ( rollno: integer, name: string, age: integer, cgpa: real) Courses ( courseno: integer, cname: string, credits: integer) Enrolled ( rollno: integer, courseno: integer, grade: string) Which of the following options is/are correct SQL query/queries to retrieve the names of the students enrolled in course number (i.e., courseno) 1470? 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 D) SELECT S.name FROM Students S NATURAL JOIN Enrolled E WHERE E.courseno = 1470;

Official answer: A) SELECT S.name FROM Students S WHERE EXISTS (SELECT * FROM Enrolled E WHERE E.courseno = 1470 AND E.rollno = S.rollno);; C) SELECT S.name FROM Students S WHERE 0; D) SELECT S.name FROM Students S NATURAL JOIN Enrolled E WHERE E.courseno = 1470;. Explanation: To retrieve the names of students enrolled in `courseno = 1470`: 1. Option (A) uses a correlated subquery with the `EXISTS` predicate. For each student tuple in `Students`, it checks whether there exists at least one record in `Enrolled` with the matching `rollno` and `courseno = 1470`. If true, `S.name` is selected. This is valid and correct. 2. Option (B) uses `SIZEOF`, which is not a standard SQL keyword or aggregate function for computing the cardinality of a subquery result. Thus, this query is syntactically invalid. 3. Option (C) uses a scalar subquery `SELECT COUNT(*) FROM Enrolled E WHERE E.courseno = 1470 AND E.rollno = S.rollno`. The condition `0 < (SELECT COUNT(*) ...)` correctly evaluates to true whenever the student has at least one enrollment record in course 1470. This is valid and correct. 4. Option (D) performs a `NATURAL JOIN` between `Students` and `Enrolled`. Since the only common attribute with the same name and type between the two tables is `rollno`, the join automatically equates `Students.rollno = Enrolled.rollno`. The `WHERE` clause then filters for `E.courseno = 1470` and projects `S.name`. This is valid and correct. Therefore, the correct options are A, C, and D.

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

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

Databases · SQL

Official IIT answer key · IIT Guwahati · Audited Aug 2026

Take topic test

GATE CSE 2025 Set 2 Q54 · MSQ · 2 marks

Consider the following relational schema: Students ( $\underline{\text{rollno: integer}}$ , name: string, age: integer, cgpa: real) Courses ( $\underline{\text{courseno: integer}}$ , cname: string, credits: integer) Enrolled ( $\underline{\text{rollno: integer}}$ , $\underline{\text{courseno: integer}}$ , grade: string) Which of the following options is/are correct SQL query/queries to retrieve the names of the students enrolled in course number (i.e., courseno) 1470?

Select one or more options

Key concept

SQL

Step-by-step verified solution

Examiner trap & misconception

Topic notes

How GATE tests SQL

In GATE CS, SQL is tested through a balanced mix of declarative query semantics, relational-algebra correspondence, subquery evaluation (correlated, nested, and universal quantification), and instance-level tracing. Questions range from conceptual integrity rules (DDL constraints, FOREIGN KEY targets, GROUP BY/HAVING rules) to practical computation of output row counts and aggregate values on small database instances. Recent papers strongly emphasize NAT execution traces and multi-correct (MSQ) equivalent query formulations.

Full SQL guide →

More on SQL

All 17 questions on SQL →

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

Databases · SQL

Official IIT answer key · IIT Guwahati · Audited Aug 2026

Take topic test

GATE CSE 2025 Set 2 Q54 · MSQ · 2 marks

Consider the following relational schema: Students ( $\underline{\text{rollno: integer}}$ , name: string, age: integer, cgpa: real) Courses ( $\underline{\text{courseno: integer}}$ , cname: string, credits: integer) Enrolled ( $\underline{\text{rollno: integer}}$ , $\underline{\text{courseno: integer}}$ , grade: string) Which of the following options is/are correct SQL query/queries to retrieve the names of the students enrolled in course number (i.e., courseno) 1470?

Select one or more options

Key concept

SQL

Step-by-step verified solution

Examiner trap & misconception

Topic notes

How GATE tests SQL

Full SQL guide →

More on SQL

All 17 questions on SQL →

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

Step-by-step verified solution

Check you can still solve SQL under a clock

More from GATE CSE 2025 Set 2

More on SQL

Step-by-step verified solution

Check you can still solve SQL under a clock

More from GATE CSE 2025 Set 2

More on SQL

Step-by-step verified solution

Check you can still solve SQL under a clock

More from GATE CSE 2025 Set 2

More on SQL

Share this solution

Step-by-step verified solution

Check you can still solve SQL under a clock

More from GATE CSE 2025 Set 2

More on SQL

Share this solution