GATE CS 2015 Set 1 — Question 61

NAT+2 / -0MediumGrouping & OrderingSQLDatabasesAggregate FunctionsSQL Joins

Databases → SQL → Aggregate Functions

Last updated 5 September 2026

Question

Consider the following relations: Student Roll No Student_Name 1 Raj 2 Rohit 3 Raj Performance Roll No Course Marks 1 Math 80 1 English 70 2 Math 75 3 English 80 2 Physics 65 3 Math 80 Consider the following SQL query. SELECT S.Student_Name, sum(P.Marks) FROM Student S, Performance P WHERE S.Roll_No = P.Roll_No GROUP BY S.Student_Name The number of rows that will be returned by the SQL query is___________.

Correct answer 2 to 2 Solution The SQL query joins the Student and Performance tables on Roll_No and then groups the results by Student_Name . 1. Join Step: Roll No 1 (Raj) matches with Math (80) and English (70). Roll No 2 (Rohit) matches with Math (75) and Physics (65). Roll No 3 (Raj) matches with English (80) and Math (80). 2. Group By Step: The grouping is done on Student_Name . The distinct student names are "Raj" and "Rohit". All records for "Raj" (from both Roll No 1 and Roll No 3) are grouped together into a single group. All records for "Rohit" are grouped into a single group. Since there are 2 distinct Student_Name values ("Raj" and "Rohit"), the query will return 2 rows. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer 2 to 2 Solution The SQL query joins the Student and Performance tables on Roll_No and then groups the results by Student_Name . 1. Join Step: Roll No 1 (Raj) matches with Math (80) and English (70). Roll No 2 (Rohit) matches with Math (75) and Physics (65). Roll No 3 (Raj) matches with English (80) and Math (80). 2. Group By Step: The grouping is done on Student_Name . The distinct student names are "Raj" and "Rohit". All records for "Raj" (from both Roll No 1 and Roll No 3) are grouped together into a single group. All records for "Rohit" are grouped into a single group. Since there are 2 distinct Student_Name values ("Raj" and "Rohit"), the query will return 2 rows.

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