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Subject: Introduction to Database Systems
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Week: 6
šÆ Session: NPTEL 2025
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NPTEL Introduction to Database Systems Week 6 Assignment Answers 2025
1. Under which of the following conditions, the update operations on views are NOT allowed?
(i) if the view definition has an aggregate operator
(ii) if the view definition includes two or more tables
(iii) if the view is defined on a single table without group by, aggregates and the SELECT clause includes the primary key of the table
- Only (ii)
- Only (iii)
- Only (i) and (ii)
- All (i), (ii) and (iii)
Answer :- For Answers Click Here
2. HAVING clause can be used in a query only if GROUP BY clause is used
- True
- False
Answer :-
3. GROUP BY clause can be used in a query only if HAVING clause is used
- True
- False
Answer :- For Answers Click Here
4. It is mandatory to use an aggregate function in a query if GROUP BY clause is used
- True
- False
Answer :-
5. Aggregate functions can be used in GROUP BY clauses
- True
- False
Answer :-
6. In which of the following SQL clauses of a main query can a sub-query be made use of ?
(i) FROM (ii) WHERE (iii) HAVING
- Only (ii)
- Only (iii)
- Only (ii) and (iii)
- All (i), (ii) and (iii)
Answer :-
7. Which of the following queries would select the courses with at least 10 āWā grades in some offering of the course ?
- SELECT courseId
FROM enrollment
WHERE grade = āWā
GROUP BY courseId
HAVING count(rollNo) >= 10 - SELECT courseId
FROM enrollment
WHERE grade = āWā
GROUP BY courseId, sem, year
HAVING count(rollNo) >= 10 - SELECT courseId
FROM enrollment
WHERE grade = āWā AND count(rollNo) >= 10
GROUP BY courseId - SELECT courseId
FROM enrollment
WHERE grade = āWā AND count(rollNo) >= 10
GROUP BY courseId, sem, year
Answer :-
8. Which of the following queries will retrieve students whose name has āpā as the second letter ?
- SELECT rollNo FROM student where name = ā_pā;
- SELECT rollNo FROM student where name LIKE ā_pā;
- SELECT rollNo FROM student where name LIKE ā_p%ā;
- SELECT rollNo FROM student where name IN ā_p%ā;
Answer :-
9. Consider two instances of the relations R1(A, B) and R2 (C, D) with the number of rows 10 and 8, respectively. What is the least possible number of tuples in the result of the following query?
SELECT *
FROM R1 FULL OUTER JOIN R2 ON R1.A = R2.C
- 0
- 18
- 8
- 10
Answer :- For Answers Click Here
10. Consider the following queries. Which of the following queries is correct to find the courses with no prerequisites?
(i) SELECT courseId
FROM preRequisite
GROUP BY courseId
HAVING count(preCourseId) = 0
(ii) SELECT courseId
FROM preRequisite a
WHERE NOT EXISTS (
SELECT preCourseId FROM preRequisite b WHERE a.courseId = b.courseId)
- Only (i)
- Only (ii)
- Both (i) and (ii)
- Neither (i) nor (ii)
Answer :-
11. Which of the following queries would find the id and name of the senior-most hod(s)?
- SELECT p1.empId, p1.name
FROM professor p1
WHERE p1.startYear IN (
SELECT min(p.startYear)
FROM professor p, department d
WHERE p.empId = d.hod) - SELECT p.empId, p.name
FROM professor p, department d
WHERE p.empId = d.hod
WHERE p.startYear IN (
SELECT min(p1.startYear)
FROM professor p1) - SELECT p1.empId, p1.name
FROM professor p1, department d1
WERE p1.empId = d1.hod
AND p1.startYear IN (
SELECT min(p.startYear)
FROM professor p, department d
WHERE p.empId = d.hod) - None of the above
Answer :-
12. Which one of the following queries would find the teacher(s) who taught CS1100 the highest number of times?
Answer :-
13. Consider the following sets about different approaches to programmatic access of databases and the properties that may apply to these approaches.
{1: Embedded SQL approach; 2: API based approach; 3: Database language approach}
{p: Only one connection to a DB server can be active at any time q: Open Database Connectivity (ODBC); r: Cursors; s: Programmers need to learn a new language ; t: Multiple connections to DB servers can be active at any time}
Identify the correct matching between the sets:
- 1āp; 2āt; 3āq
- 1āt; 2āq; 3ās
- 1ās; 2ār; 3āp
- 1āp; 2āt; 3ās
Answer :- For Answers Click Here
Introduction to Database Systems Week 6 NPTEL Assignment Answers 2024
1. Which of the following SQL clauses can have a subquery?
(i) FROM (ii) GROUP BY (iii) HAVING
- Only (i)
- Only (i) and (ii)
- Only (i) and (iii)
- All (i), (ii) and (iii)
Answer :- c
2. Views can never be used in an update query
- True
- False
Answer :- b
3. Views are materialized into tables if the view definition has only one table
- True
- False
Answer :- b
Forests and Their Management Week 6 NPTEL Assignment Answers
4. Views can be used in the definition of other views
- True
- False
Answer :- a
5. Aggregate operators can be used to define views
- True
- False
Consider the relation stud (C1, C2, C3, C4, C5, C6). A SQL query Q created using stud has the columns C1, C2, and C3 in the group by clause. Assuming Q is a syntactically correct query,state whether the following statements are true or false.
Answer :- a
6. The column C4 can be used in the HAVING clause without aggregate operator
- True
- False
Answer :- b
7. The column C4 can be used in the WHERE clause without aggregate operator
- True
- False
Answer :- a
8. The column C3 can be used in the SELECT clause without aggregate operator
- True
- False
Answer :- a
9. The column C3 can be used in the SELECT clause with aggregate operator
- True
- False
Answer :- b
10. Consider the following schema of the relation stud:
stud(ā K ā , C1)
Which of the following queries would find the number of NULLs in the column C1 of the stud relation.
- SELECT COUNT(C1) FROM stud WHERE C1 IS NOT NULL
- SELECT COUNT(*) – COUNT(C1) FROM stud WHERE C1 IS NOT NULL
- SELECT COUNT() FROM stud WHERE C1 = NULL
- SELECT COUNT(*) – COUNT(C1) FROM stud
Answer :- d
11. Consider two instances of the relations R1 and R2 with the number of rows 10 and 8, respectively. The minimum number of tuples in the result of the following query is
SELECT *
FROM R1 FULL OUTER JOIN R2
- 10
- 98
- 80
- 18
Answer :- a
12. DLETE keyword can be used to do which of the following operations?
(i) delete all rows (ii) delete specific rows (iii) delete table definition
- Only (ii)
- Only (iii)
- Only (i) and (ii)
- All (i), (ii) and (iii)
Answer :- c
13.
Answer :- d
14. Consider the following query
select deptNo
from course
group by deptNo
having sum(credits) >= ANY (select max(x.totalCredits)
from ( select sum(credits) as totalCredits
from course
group by deptNo) as x
);
Suppose total-credits of a department is the sum of the credits of the courses offered by the department. Which of the following statements is correct about the above query?
- It finds the department(s) with the highest number of total-credits across all the departments.
- It finds the department(s) with total-credits greater than or equal to the sum of the total-credits of all the departments.
- It finds the department(s) with total-credits greater than or equal to the credits of the course with the highest number of credits across the institute.
- It lists all the departments in the institute.
Answer :- a
15. Which one of the following queries would find the senior-most professor(s) of each department?
Answer :- b
16. Consider the following sets about different approaches to programmatic access of databases and the properties that may apply to these approaches.
{1: Embedded SQL approach; 2: API based approach; 3: Database language approach}
{p: Syntax-check during compilation q: driver; r: cursors; s: No impedance mismatch; t: Multiple active connections }
Identify the correct matching between the sets:
- 1–p; 2–t; 3–q
- 1–t; 2–q; 3–s
- 1–s; 2–q; 3–t
- 1–p; 2–t; 3–s
Answer :- d
Conclusion:
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