CBSE Class 12

Q-1

How many students scored more than 80 marks?

Medium SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT COUNT(*) FROM STUDENT WHERE Marks > 80;

Answer: 3

Explanation: Amit, Neha, Sita → 3 students.

Q-2

Which students belong to Class XII?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE Class='XII';

Answer: Amit, Neha, Sita

Explanation: Three students are in XII.

Q-3

What is the highest marks?

Easy Functions

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT MAX(Marks) FROM STUDENT;

Answer: 92

Explanation: Max marks = 92.

Q-4

Which students are from Mumbai?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE City='Mumbai';

Answer: Neha and Arun

Explanation: Neha and Arun.

Q-5

How many students are in Delhi?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT COUNT(*) FROM STUDENT WHERE City='Delhi';

Answer: 2

Explanation: Amit and Ravi → 2.

Q-6

Which students have marks equal to 85?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE Marks=85;

Answer: Amit and Sita

Explanation: Two students scored 85.

Q-7

Which students scored below 70?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE Marks<70;

Answer: Arun

Explanation: Only Arun has 60.

Q-8

Which city has the highest number of students?

Medium GROUP BY

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT City, COUNT(*) FROM STUDENT GROUP BY City;

Answer: Both Delhi and Mumbai

Explanation: Delhi=2, Mumbai=2.

Q-9

Which student has the lowest marks?

Medium Subquery

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE Marks=(SELECT MIN(Marks) FROM STUDENT);

Answer: Arun

Explanation: Arun has 60.

Q-10

Which students are enrolled in Math?

Medium JOIN

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT Name FROM STUDENT S JOIN COURSE C ON S.RollNo=C.RollNo WHERE Course='Math';

Answer: Amit and Sita

Explanation: RollNo 1 and 4 → Amit, Sita.

Q-11

How many distinct cities are present?

Medium SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT COUNT(DISTINCT City) FROM STUDENT;

Answer: 3

Explanation: Cities: Delhi, Mumbai, Chennai → 3.

Q-12

Which students scored marks between 70 and 90?

Medium SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE Marks BETWEEN 70 AND 90;

Answer: Amit, Ravi, Sita

Explanation: Marks 70–90 → Amit (85), Ravi (75), Sita (85).

Q-13

What will be the output?

Medium Functions

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT SUM(Marks) FROM STUDENT WHERE Class='XII';

Answer: 262

Explanation: 85 + 92 + 85 = 262.

Q-14

Which students are NOT from Delhi?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE City <> 'Delhi';

Answer: Neha, Sita, Arun

Explanation: Exclude Delhi → Neha, Sita, Arun.

Q-15

How many courses is Amit enrolled in?

Medium JOIN

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT COUNT(*) FROM COURSE WHERE RollNo=1;

Answer: 2

Explanation: Amit (RollNo=1) → Math, Chemistry → 2.

Q-16

Which student is enrolled in Biology?

Medium JOIN

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT Name FROM STUDENT S JOIN COURSE C ON S.RollNo=C.RollNo WHERE Course='Biology';

Answer: Ravi

Explanation: RollNo 3 → Ravi.

Q-17

Which class has more students?

Medium GROUP BY

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Class, COUNT(*) FROM STUDENT GROUP BY Class;

Answer: XII

Explanation: XII=3, XI=2.

Q-18

Which students have marks equal to the maximum?

Medium Subquery

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT Name FROM STUDENT WHERE Marks=(SELECT MAX(Marks) FROM STUDENT);

Answer: Neha

Explanation: Neha has highest marks.

Q-19

How many students are enrolled in at least one course?

Medium JOIN

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT COUNT(DISTINCT RollNo) FROM COURSE;

Answer: 4

Explanation: RollNos: 1,2,3,4 → 4 students.

Q-20

Which student has no course assigned?

Hard Subquery

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT Name FROM STUDENT WHERE RollNo NOT IN (SELECT RollNo FROM COURSE);

Answer: Arun

Explanation: Arun (RollNo 5) not in COURSE.

Q-21

What will be the output of the query?

Medium SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT COUNT(*) FROM COURSE WHERE RollNo=1;

Answer: 2

Explanation: RollNo 1 appears twice.

Q-22

Which students have taken more than one course?

Hard GROUP BY

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT Name FROM STUDENT WHERE RollNo IN (SELECT RollNo FROM COURSE GROUP BY RollNo HAVING COUNT(*)>1);

Answer: Amit

Explanation: Only Amit has 2 courses.

Q-23

What will be the output?

Medium Functions

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT MIN(Marks) FROM STUDENT WHERE Class='XI';

Answer: 60

Explanation: XI → Ravi(75), Arun(60) → min=60.

Q-24

Which students have not taken any course?

Medium Subquery

Sample Data

– STUDENT + COURSE TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

CID	Course	RollNo
101	Math	1
102	Physics	2
103	Chemistry	1
104	Biology	3
105	Math	4

Reference Code

SELECT Name FROM STUDENT WHERE RollNo NOT IN (SELECT RollNo FROM COURSE);

Answer: Arun

Explanation: Arun (RollNo 5) not present in COURSE.

Q-25

What is the total marks of students from Delhi?

Medium Functions

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 101 | Math | 1 | | 102 | Physics | 2 | | 103 | Chemistry | 1 | | 104 | Biology | 3 | | 105 | Math | 4 |

Reference Code

SELECT SUM(Marks) FROM STUDENT WHERE City='Delhi';

Answer: 160

Explanation: 85 + 75 = 160.

Q-26

Which SQL clause is used to filter grouped data?

Easy Theory

Sample Data

– STUDENT TABLE (same as above)

Answer: HAVING

Explanation: HAVING filters grouped results.

Q-27

Which operator combines two SELECT queries removing duplicates?

Medium Operations

Sample Data

– STUDENT TABLE (same as above)

Answer: UNION

Explanation: UNION removes duplicates.

Q-28

Which clause is used to sort in descending order?

Easy Theory

Sample Data

– STUDENT TABLE (same as above)

Answer: DESC

Explanation: DESC sorts descending.

Q-29

Which function returns number of rows?

Easy Functions

Sample Data

– STUDENT TABLE (same as above)

Answer: COUNT()

Explanation: COUNT counts rows.

Q-30

Which key ensures uniqueness and cannot be NULL?

Easy Constraints

Sample Data

– STUDENT TABLE (same as above)

Answer: PRIMARY KEY

Explanation: Primary key is unique and not NULL.

Q-31

Which SQL statement modifies data?

Easy DML

Sample Data

– STUDENT TABLE (same as above)

Answer: UPDATE

Explanation: UPDATE modifies records.

Q-32

Which clause specifies table name?

Easy SQL Basics

Sample Data

– STUDENT TABLE (same as above)

Answer: FROM

Explanation: FROM specifies table.

Q-33

Which function returns smallest value?

Easy Functions

Sample Data

– STUDENT TABLE (same as above)

Answer: MIN()

Explanation: MIN returns smallest.

Q-34

Which clause removes duplicate rows?

Easy SQL Query

Sample Data

– STUDENT TABLE (same as above)

Answer: DISTINCT

Explanation: DISTINCT removes duplicates.

Q-35

Which SQL statement deletes rows?

Easy DML

Sample Data

– STUDENT TABLE (same as above)

Answer: DELETE

Explanation: DELETE removes rows.

Q-36

Which clause groups rows?

Easy GROUP BY

Sample Data

– STUDENT TABLE (same as above)

Answer: GROUP BY

Explanation: GROUP BY groups rows.

Q-37

Which SQL clause filters rows before grouping?

Medium SQL Query

Sample Data

– STUDENT TABLE (same as above)

Answer: WHERE

Explanation: WHERE filters before grouping.

Q-38

Which clause is executed after GROUP BY?

Hard Execution Order

Sample Data

– STUDENT TABLE (same as above)

Answer: HAVING

Explanation: HAVING comes after GROUP BY.

Q-39

Which join returns only matching rows?

Medium JOIN

Sample Data

– STUDENT TABLE (same as above)

Answer: INNER JOIN

Explanation: INNER JOIN returns matching rows.

Q-40

Which SQL clause is used to rename columns?

Easy SQL Query

Sample Data

– STUDENT TABLE (same as above)

Answer: AS

Explanation: AS is used for alias.

Q-41

You need to display names of students who scored more than 80 marks. Which SQL query is correct?

Easy SQL Query

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi | | 4 | Sita | XII | 85 | Chennai | | 5 | Arun | XI | 60 | Mumbai |

Answer: SELECT Name FROM STUDENT WHERE Marks > 80;

Explanation: Condition strictly greater than 80 is required.

Q-42

You want to count how many students are in each city. Which query is correct?

Medium GROUP BY

Sample Data

– STUDENT TABLE (same as above)

Answer: SELECT City, COUNT(*) FROM STUDENT GROUP BY City;

Explanation: Grouping by City is required to count per city.

Q-43

Find names of students who scored the highest marks. Which query is correct?

Medium Subquery

Sample Data

– STUDENT TABLE (same as above)

Answer: SELECT Name FROM STUDENT WHERE Marks = (SELECT MAX(Marks) FROM STUDENT);

Explanation: MAX must be computed using subquery.

Q-44

You need to display student names and their courses using both tables. Which query is correct?

Medium JOIN

Sample Data

– STUDENT + COURSE TABLE (same as above)

Answer: SELECT Name, Course FROM STUDENT S JOIN COURSE C ON S.RollNo=C.RollNo;

Explanation: JOIN must use matching RollNo.

Q-45

You want to find students who are NOT from Delhi. Which query is correct?

Medium SQL Query

Sample Data

– STUDENT TABLE (same as above)

Answer: SELECT Name FROM STUDENT WHERE City != 'Delhi';

Explanation: != or <> works, but only option A is syntactically correct here.

Q-46

You need to find number of courses taken by each student. Which query is correct?

Medium GROUP BY

Sample Data

– COURSE TABLE (same as above)

Answer: SELECT RollNo, COUNT(*) FROM COURSE GROUP BY RollNo;

Explanation: Group by RollNo to count per student.

Q-47

You want names of students who are enrolled in at least one course. Which query is correct?

Hard Subquery

Sample Data

– STUDENT + COURSE TABLE (same as above)

Answer: SELECT Name FROM STUDENT WHERE RollNo IN (SELECT RollNo FROM COURSE);

Explanation: Subquery fetches valid RollNos.

Q-48

You want to display cities having more than one student. Which query is correct?

Hard GROUP BY

Sample Data

– STUDENT TABLE (same as above)

Answer: SELECT City FROM STUDENT GROUP BY City HAVING COUNT(*)>1;

Explanation: HAVING filters grouped data.

Q-49

You want to find total marks of students from Mumbai. Which query is correct?

Easy Functions

Sample Data

– STUDENT TABLE (same as above)

Answer: SELECT SUM(Marks) FROM STUDENT WHERE City='Mumbai';

Explanation: SUM calculates total marks.

Q-50

You want names of students sorted by marks in descending order. Which query is correct?

Easy ORDER BY

Sample Data

– STUDENT TABLE (same as above)

Answer: SELECT Name FROM STUDENT ORDER BY Marks DESC;

Explanation: DESC is used for descending order.

Q-51

What is the error in the following query? SELECT Name FROM STUDENT WHERE Marks = MAX(Marks);

Medium Debug SQL

Sample Data

– STUDENT TABLE | RollNo | Name | Class | Marks | City | |——–|——|——-|——-|——| | 1 | Amit | XII | 85 | Delhi | | 2 | Neha | XII | 92 | Mumbai | | 3 | Ravi | XI | 75 | Delhi |

Reference Code

SELECT Name FROM STUDENT WHERE Marks = MAX(Marks);

Answer: MAX() cannot be used in WHERE directly

Explanation: Aggregate functions require subqueries or HAVING.

Q-52

What is wrong with this query? SELECT City, COUNT(*) FROM STUDENT;

Medium Debug SQL

Sample Data

– STUDENT TABLE (same as above)

Reference Code

SELECT City, COUNT(*) FROM STUDENT;

Answer: Missing GROUP BY clause

Explanation: GROUP BY City is required.

Q-53

Identify the issue: SELECT Name FROM STUDENT WHERE City = Delhi;

Easy Debug SQL

Sample Data

– STUDENT TABLE (same as above)

Reference Code

SELECT Name FROM STUDENT WHERE City = Delhi;

Answer: String value not in quotes

Explanation: Strings must be in quotes.

Q-54

What is wrong? SELECT * FROM STUDENT GROUP BY Name;

Hard Debug SQL

Sample Data

– STUDENT TABLE (same as above)

Reference Code

SELECT * FROM STUDENT GROUP BY Name;

Answer: SELECT * cannot be used with GROUP BY

Explanation: All selected columns must be grouped or aggregated.

Q-55

What is wrong in this query? SELECT Name FROM STUDENT WHERE Marks > AVG(Marks);

Medium Debug SQL

Sample Data

– STUDENT TABLE (same as above)

Reference Code

SELECT Name FROM STUDENT WHERE Marks > AVG(Marks);

Answer: Aggregate in WHERE without subquery

Explanation: AVG must be inside subquery.

Q-56

Find students who scored above average marks. Which query is correct?

Medium Case Study

Sample Data

– STUDENT TABLE | RollNo | Name | Marks | |——–|——|——-| | 1 | Amit | 85 | | 2 | Neha | 92 | | 3 | Ravi | 75 | | 4 | Sita | 85 |

Answer: SELECT Name FROM STUDENT WHERE Marks > (SELECT AVG(Marks) FROM STUDENT);

Explanation: Subquery required.

Q-57

Find cities having more than one student.

Medium Case Study

Sample Data

– STUDENT TABLE | RollNo | Name | City | |——–|——|——| | 1 | A | Delhi | | 2 | B | Delhi | | 3 | C | Mumbai | | 4 | D | Mumbai |

Answer: SELECT City FROM STUDENT GROUP BY City HAVING COUNT(*)>1;

Explanation: HAVING filters grouped rows.

Q-58

Find students who are not enrolled in any course.

Medium Case Study

Sample Data

– STUDENT + COURSE TABLE (same pattern)

Answer: SELECT Name FROM STUDENT WHERE RollNo NOT IN (SELECT RollNo FROM COURSE);

Explanation: NOT IN identifies missing entries.

Q-59

Find number of courses per student.

Easy Case Study

Sample Data

– COURSE TABLE | CID | Course | RollNo | |—–|——–|——–| | 1 | Math | 1 | | 2 | Physics | 1 | | 3 | Bio | 2 |

Answer: SELECT RollNo, COUNT(*) FROM COURSE GROUP BY RollNo;

Explanation: Grouping needed per RollNo.

Q-60

Find names and courses of students.

Medium Case Study

Sample Data

– STUDENT + COURSE TABLE

Answer: SELECT Name, Course FROM STUDENT S JOIN COURSE C ON S.RollNo=C.RollNo;

Explanation: JOIN required.

Q-61

Find highest marks in each class.

Medium Case Study

Sample Data

– STUDENT TABLE

Answer: SELECT Class, MAX(Marks) FROM STUDENT GROUP BY Class;

Explanation: Group by Class.

Q-62

Find students whose marks are equal to minimum marks.

Medium Case Study

Sample Data

– STUDENT TABLE

Answer: SELECT Name FROM STUDENT WHERE Marks = (SELECT MIN(Marks) FROM STUDENT);

Explanation: Subquery required.

Q-63

Find total marks of all students.

Easy Case Study

Sample Data

– STUDENT TABLE

Answer: SELECT SUM(Marks) FROM STUDENT;

Explanation: SUM gives total.

Q-64

Find students sorted by marks descending.

Easy Case Study

Sample Data

– STUDENT TABLE

Answer: SELECT Name FROM STUDENT ORDER BY Marks DESC;

Explanation: DESC sorts descending.

Q-65

Find distinct cities.

Easy Case Study

Sample Data

– STUDENT TABLE

Answer: SELECT DISTINCT City FROM STUDENT;

Explanation: DISTINCT removes duplicates.

Computer Science

09 Structured Query Language (SQL)