Consider the following tables (relations): Primary keys in the tables are…
2018
Consider the following tables (relations):
Primary keys in the tables are shown using underline. Now, consider the following query:
SELECT S.Name, Sum (P.Marks) FROM Students S , Performance P WHERE S.Roll-No=P.Roll-No
GROUP BY S.Name
The number of rows returned by the above query is
- A.
0
- B.
1
- C.
2
- D.
3
Attempted by 357 students.
Show answer & explanation
Correct answer: C
Key idea: join Students with Performance on Roll-No, then group the results by student name. Students who share the same name are combined into a single group.
Step-by-step calculation:
For roll number 18CS101 (Name: Ramesh): Marks = 60 + 65 = 125
For roll number 18CS102 (Name: Mukesh): Marks = 80 + 75 = 155
For roll number 18CS103 (Name: Ramesh): Marks = 85 + 70 = 155
Now group these results by student name:
Ramesh: 125 (from 18CS101) + 155 (from 18CS103) = 280
Mukesh: 155 (from 18CS102)
Final answer: The query returns 2 rows (one for Ramesh and one for Mukesh).
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