CBSE Class 12

Q-1

How many rows are present in the STUDENT table?

Easy SQL General

Sample Data

RollNo	Name	Class
1	Amit	XII
2	Neha	XII
3	Ravi	XI

Reference Code

SELECT COUNT(*) FROM STUDENT;

Answer: 3

Explanation: COUNT(*) returns the total number of rows in the table, which is 3.

Q-2

Which rows are selected by the following query?

Easy SQL Query

Sample Data

RollNo	Name	Marks
1	Amit	85
2	Neha	65
3	Ravi	75

Reference Code

SELECT * FROM STUDENT WHERE Marks >= 75;

Answer: Amit and Ravi

Explanation: The WHERE clause selects rows with Marks greater than or equal to 75, which are Amit and Ravi.

Q-3

How many distinct classes are present in the table?

Easy SQL Function

Sample Data

RollNo	Class
1	XII
2	XII
3	XI

Reference Code

SELECT COUNT(DISTINCT Class) FROM STUDENT;

Answer: 2

Explanation: There are two distinct values in the Class column: XI and XII.

Q-4

Which value will be returned by the query?

Easy SQL Function

Sample Data

RollNo	Marks
1	60
2	80
3	70

Reference Code

SELECT MAX(Marks) FROM STUDENT;

Answer: 80

Explanation: MAX() returns the highest value in the Marks column, which is 80.

Q-5

How many rows are selected by the query?

Easy SQL Query

Sample Data

EmpID	Dept
1	IT
2	HR
3	IT

Reference Code

SELECT * FROM EMP WHERE Dept = 'IT';

Answer: 2

Explanation: There are two employees whose department is IT.

Q-6

Which value is ignored by aggregate functions such as SUM and AVG?

Easy SQL Aggregation

Answer: NULL

Explanation: Aggregate functions ignore NULL values during calculation.

Q-7

How many groups are formed by the query?

Easy SQL Grouping

Sample Data

EmpID	Dept
1	Sales
2	HR
3	Sales
4	HR

Reference Code

SELECT Dept FROM EMP GROUP BY Dept;

Answer: 2

Explanation: There are two distinct department values: Sales and HR.

Q-8

Which clause is used to sort the result of a query?

Easy SQL General

Answer: ORDER BY

Explanation: ORDER BY is used to sort query results.

Q-9

Which value will be returned by the query?

Easy SQL Aggregation

Sample Data

Num
10
20
30

Reference Code

SELECT SUM(Num) FROM T;

Answer: 60

Explanation: SUM adds all numeric values: 10 + 20 + 30 = 60.

Q-10

Which clause is used to select rows based on a condition?

Easy SQL Query

Answer: WHERE

Explanation: WHERE is used to filter rows based on conditions.

Q-11

Which classes will appear in the output of the query?

Medium SQL Grouping

Sample Data

RollNo	Class	Marks
1	XI	55
2	XI	75
3	XII	80
4	XII	60

Reference Code

SELECT Class
FROM STUDENT
WHERE Marks >= 60
GROUP BY Class;

Answer: XI and XII

Explanation: WHERE filters rows first. Both XI and XII have at least one student with Marks ≥ 60.

Q-12

How many rows are counted by the aggregate function?

Medium SQL Aggregation

Sample Data

EmpID	Dept	Salary
1	IT	40000
2	IT	NULL
3	HR	30000
4	HR	30000

Reference Code

SELECT COUNT(Salary) FROM EMP;

Answer: 3

Explanation: COUNT(column) ignores NULL values, so three non-NULL salaries are counted.

Q-13

How many groups are formed by the query?

Medium SQL Grouping

Sample Data

EmpID	Dept	Location
1	IT	Delhi
2	IT	Mumbai
3	HR	Delhi
4	HR	Delhi

Reference Code

SELECT Dept, Location
FROM EMP
GROUP BY Dept, Location;

Answer: 3

Explanation: Distinct (Dept, Location) pairs are (IT, Delhi), (IT, Mumbai), and (HR, Delhi).

Q-14

Which departments satisfy the condition in the query?

Medium SQL Aggregation

Sample Data

EmpID	Dept	Salary
1	IT	30000
2	IT	30000
3	HR	40000

Reference Code

SELECT Dept
FROM EMP
GROUP BY Dept
HAVING SUM(Salary) >= 60000;

Answer: IT only

Explanation: IT has a total salary of 60000, which satisfies the HAVING condition; HR does not.

Q-15

Which rows are excluded before grouping is applied?

Medium SQL Query

Sample Data

RollNo	Class	Marks
1	XI	45
2	XI	65
3	XII	75
4	XII	55

Reference Code

SELECT Class, AVG(Marks)
FROM STUDENT
WHERE Marks >= 60
GROUP BY Class;

Answer: Marks < 60

Explanation: WHERE removes rows with Marks less than 60 before GROUP BY is applied.

Q-16

What value will be returned by the query?

Medium SQL Function

Sample Data

Value
10
20
NULL
30

Reference Code

SELECT AVG(Value) FROM T;

Answer: 20

Explanation: AVG ignores NULL values, so (10 + 20 + 30) / 3 = 20.

Q-17

Which query correctly filters aggregated results?

Medium SQL Error Analysis

Answer: GROUP BY Dept HAVING COUNT(*) > 1

Explanation: HAVING is used to apply conditions on grouped (aggregated) data.

Q-18

Which values are counted by COUNT(DISTINCT Dept)?

Medium SQL Function

Sample Data

EmpID	Dept
1	IT
2	IT
3	HR
4	HR

Reference Code

SELECT COUNT(DISTINCT Dept) FROM EMP;

Answer: 2

Explanation: COUNT(DISTINCT Dept) counts unique department values: IT and HR.

Q-19

Which clause is evaluated after GROUP BY but before ORDER BY?

Medium SQL General

Answer: HAVING

Explanation: HAVING is evaluated after GROUP BY and before ORDER BY.

Q-20

Which query will result in a syntax error?

Medium SQL Error Analysis

Answer: SELECT Class, Marks FROM STUDENT GROUP BY Class

Explanation: Marks is neither aggregated nor included in GROUP BY, causing a syntax error.

Q-21

Which departments will appear in the output?

Hard SQL Grouping

Sample Data

EmpID	Dept	Salary
1	IT	50000
2	IT	20000
3	HR	30000
4	HR	30000

Reference Code

SELECT Dept
FROM EMP
WHERE Salary >= 30000
GROUP BY Dept
HAVING COUNT(*) > 1;

Answer: HR only

Explanation: WHERE keeps rows with Salary ≥ 30000. HR has two such rows, IT has only one. HAVING COUNT(*) > 1 keeps only HR.

Q-22

How many rows will be returned by the query?

Hard SQL Aggregation

Sample Data

RollNo	Class	Marks
1	XII	80
2	XII	60
3	XII	40
4	XI	90

Reference Code

SELECT Class, COUNT(*)
FROM STUDENT
WHERE Marks >= 50
GROUP BY Class
HAVING COUNT(*) >= 2;

Answer: 0

Explanation: After WHERE, Class XII has two rows, Class XI has one. HAVING COUNT(*) ≥ 2 keeps only Class XII, producing one row.

Q-23

Which value will be returned by the query?

Hard SQL Function

Sample Data

Value
10
10
20
NULL

Reference Code

SELECT AVG(DISTINCT Value) FROM T;

Answer: 15

Explanation: DISTINCT removes duplicate 10; NULL is ignored. AVG of (10, 20) = 15.

Q-24

How many groups are formed by the query?

Hard SQL Grouping

Sample Data

EmpID	Dept	Gender
1	IT	M
2	IT	F
3	IT	M
4	HR	F

Reference Code

SELECT Dept, Gender
FROM EMP
GROUP BY Dept, Gender;

Answer: 3

Explanation: Distinct (Dept, Gender) pairs are (IT,M), (IT,F), and (HR,F) — three groups.

Q-25

Which students are counted by the aggregate function?

Hard SQL Aggregation

Sample Data

RollNo	Marks
1	90
2	NULL
3	70
4	NULL

Reference Code

SELECT COUNT(Marks) FROM STUDENT;

Answer: Only students with non-NULL marks

Explanation: COUNT(column) ignores NULL values and counts only rows with actual marks.

Q-26

Which query correctly produces department-wise average salary greater than 35000?

Hard SQL Error Analysis

Answer: GROUP BY Dept HAVING AVG(Salary) > 35000

Explanation: Aggregate conditions must be written using HAVING after GROUP BY.

Q-27

Which value is returned by the query?

Hard SQL Function

Sample Data

Num
-10
5
15

Reference Code

SELECT MIN(Num) FROM T;

Answer: -10

Explanation: MIN returns the smallest numeric value, including negative numbers.

Q-28

Which rows are eliminated before grouping occurs?

Hard SQL Query

Sample Data

RollNo	Class	Marks
1	XII	80
2	XII	40
3	XI	90

Reference Code

SELECT Class, AVG(Marks)
FROM STUDENT
WHERE Marks > 50
GROUP BY Class;

Answer: Rows with Marks ≤ 50

Explanation: WHERE is applied before GROUP BY, so rows with Marks ≤ 50 are removed.

Q-29

How many rows will be produced by the query?

Hard SQL Aggregation

Sample Data

EmpID	Dept
1	IT
2	IT
3	IT
4	HR

Reference Code

SELECT Dept, COUNT(*)
FROM EMP
GROUP BY Dept
HAVING COUNT(*) > 2;

Answer: 1

Explanation: Only IT has more than two employees, so only one row is returned.

Q-30

Which statement about SQL execution order is correct?

Hard SQL General

Answer: WHERE is evaluated before GROUP BY

Explanation: WHERE filters rows before GROUP BY and HAVING are applied.

Q-31

How many records are returned by the query?

Easy SQL Query

Sample Data

RollNo	Name	Class
1	Anu	XI
2	Binu	XII
3	Chetan	XI

Reference Code

SELECT * FROM STUDENT WHERE Class='XI';

Answer: 2

Explanation: There are two students whose Class is XI.

Q-32

Which value will be returned by the query?

Easy SQL Function

Sample Data

Marks
55
65
75

Reference Code

SELECT MIN(Marks) FROM STUDENT;

Answer: 55

Explanation: MIN() returns the smallest value, which is 55.

Q-33

How many distinct departments are present?

Easy SQL Function

Sample Data

EmpID	Dept
1	Sales
2	HR
3	Sales
4	IT

Reference Code

SELECT COUNT(DISTINCT Dept) FROM EMP;

Answer: 3

Explanation: Distinct department values are Sales, HR, and IT.

Q-34

Which rows are selected by the query?

Easy SQL Query

Sample Data

RollNo	Marks
1	40
2	60
3	80

Reference Code

SELECT * FROM STUDENT WHERE Marks > 50;

Answer: RollNo 2 and 3

Explanation: Rows with Marks greater than 50 are selected: RollNo 2 and 3.

Q-35

How many groups are formed by the query?

Easy SQL Grouping

Sample Data

EmpID	Dept
1	HR
2	HR
3	HR

Reference Code

SELECT Dept FROM EMP GROUP BY Dept;

Answer: 1

Explanation: There is only one distinct department value: HR.

Q-36

Which clause is used to display unique values?

Easy SQL General

Answer: DISTINCT

Explanation: DISTINCT removes duplicate values from the result.

Q-37

Which value will be returned by the query?

Easy SQL Function

Sample Data

Salary
25000
30000
45000

Reference Code

SELECT MAX(Salary) FROM EMP;

Answer: 45000

Explanation: MAX() returns the highest salary value, which is 45000.

Q-38

Which clause is used to filter rows based on a condition?

Easy SQL Query

Answer: WHERE

Explanation: WHERE filters rows based on conditions.

Q-39

How many values are added by the aggregate function?

Easy SQL Aggregation

Sample Data

Num
5
10
15

Reference Code

SELECT SUM(Num) FROM T;

Answer: 30

Explanation: SUM adds all values: 5 + 10 + 15 = 30.

Q-40

Which clause is used to arrange the output in ascending or descending order?

Easy SQL General

Answer: ORDER BY

Explanation: ORDER BY is used to sort query results.

Q-41

Which departments will appear in the output of the query?

Medium SQL Grouping

Sample Data

EmpID	Dept	Salary
1	IT	40000
2	IT	20000
3	HR	30000

Reference Code

SELECT Dept
FROM EMP
WHERE Salary >= 30000
GROUP BY Dept;

Answer: IT and HR

Explanation: WHERE filters rows first. IT (40000) and HR (30000) both satisfy the condition.

Q-42

How many values are considered while computing the average?

Medium SQL Aggregation

Sample Data

Value
10
NULL
20
30

Reference Code

SELECT AVG(Value) FROM T;

Answer: 3

Explanation: AVG ignores NULL values, so only three values are considered.

Q-43

How many groups will be formed by the query?

Medium SQL Grouping

Sample Data

EmpID	Dept	Location
1	IT	Delhi
2	IT	Delhi
3	IT	Mumbai
4	HR	Delhi

Reference Code

SELECT Dept, Location
FROM EMP
GROUP BY Dept, Location;

Answer: 3

Explanation: Distinct (Dept, Location) pairs are (IT, Delhi), (IT, Mumbai), and (HR, Delhi).

Q-44

Which classes satisfy the condition in the query?

Medium SQL Aggregation

Sample Data

RollNo	Class	Marks
1	XI	70
2	XI	80
3	XII	60
4	XII	65

Reference Code

SELECT Class
FROM STUDENT
GROUP BY Class
HAVING AVG(Marks) >= 70;

Answer: XI only

Explanation: Average of XI is 75, while average of XII is 62.5. Only XI satisfies the condition.

Q-45

Which rows are removed before grouping is applied?

Medium SQL Query

Sample Data

RollNo	Class	Marks
1	XI	45
2	XI	65
3	XII	75
4	XII	55

Reference Code

SELECT Class, COUNT(*)
FROM STUDENT
WHERE Marks > 50
GROUP BY Class;

Answer: Rows with Marks ≤ 50

Explanation: WHERE clause removes rows with Marks less than or equal to 50 before grouping.

Q-46

What will be the output of the query?

Medium SQL Function

Sample Data

Num
5
5
10

Reference Code

SELECT SUM(DISTINCT Num) FROM T;

Answer: 15

Explanation: DISTINCT removes duplicate 5. SUM of 5 and 10 is 15.

Q-47

Which clause should be used to filter grouped data?

Medium SQL General

Answer: HAVING

Explanation: HAVING is used to filter grouped (aggregated) data.

Q-48

Which query will result in a syntax error?

Medium SQL Error Analysis

Answer: SELECT Dept, Salary FROM EMP GROUP BY Dept

Explanation: Salary is neither aggregated nor included in GROUP BY.

Q-49

Which value is returned by the query?

Medium SQL Function

Sample Data

Num
-5
0
10

Reference Code

SELECT MAX(Num) FROM T;

Answer: 10

Explanation: MAX returns the highest numeric value, which is 10.

Q-50

Which clause is evaluated immediately after GROUP BY?

Medium SQL General

Answer: HAVING

Explanation: HAVING is evaluated after GROUP BY and before ORDER BY.

Informatics Practices

01 Querying and SQL Functions