CBSE Class 12 Computer Science – Detailed SQL Code Examples (2025-2026)

Most Important SQL Topics (2021–2025 PYQs Trend)

DDL: CREATE, ALTER, DROP, TRUNCATE
DML: INSERT, UPDATE, DELETE
DQL: SELECT with WHERE, ORDER BY, GROUP BY, HAVING
Joins: INNER JOIN, LEFT JOIN, RIGHT JOIN
Aggregate Functions: COUNT, SUM, AVG, MAX, MIN
Subqueries & Nested Queries
Constraints: PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL
Normalization & Keys

Detailed SQL Code Examples – Most Repeated Questions

1. Table Creation & Constraints

                
-- Create Employee Table with Constraints
CREATE TABLE Employee (
    EmpID INT PRIMARY KEY AUTO_INCREMENT,
    EmpName VARCHAR(50) NOT NULL,
    Salary DECIMAL(10,2),
    DeptID INT,
    HireDate DATE DEFAULT CURRENT_DATE,
    Email VARCHAR(100) UNIQUE,
    FOREIGN KEY (DeptID) REFERENCES Department(DeptID)
    ON DELETE SET NULL
    ON UPDATE CASCADE
);
                
            

2. Insert, Update, Delete

                
-- Insert Multiple Records
INSERT INTO Employee (EmpName, Salary, DeptID, Email) VALUES
('Rahul Sharma', 65000.00, 101, 'rahul@company.com'),
('Priya Singh', 72000.00, 102, 'priya@company.com');

-- Update Salary for Employees in Dept 101
UPDATE Employee
SET Salary = Salary + 5000
WHERE DeptID = 101;

-- Delete Employee with EmpID 5
DELETE FROM Employee WHERE EmpID = 5;
                
            

3. SELECT Queries – Most Important

                
-- Basic SELECT with WHERE & ORDER BY
SELECT EmpName, Salary 
FROM Employee 
WHERE Salary > 50000 
ORDER BY Salary DESC;

-- Aggregate Functions with GROUP BY & HAVING
SELECT DeptID, COUNT(*) AS TotalEmployees, AVG(Salary) AS AvgSalary
FROM Employee 
GROUP BY DeptID 
HAVING COUNT(*) > 2;

-- JOIN Example (Inner Join)
SELECT e.EmpName, d.DeptName, e.Salary
FROM Employee e
INNER JOIN Department d ON e.DeptID = d.DeptID
WHERE d.DeptName = 'IT';

-- Subquery Example – Employees with Salary > Average Salary
SELECT EmpName, Salary
FROM Employee
WHERE Salary > (SELECT AVG(Salary) FROM Employee);
                
            

4. Advanced Queries – Very High Repeat

                
-- Second Highest Salary
SELECT MAX(Salary) AS SecondHighest
FROM Employee
WHERE Salary < (SELECT MAX(Salary) FROM Employee);

-- Employees earning more than their Department Average
SELECT e.EmpName, e.Salary, d.DeptName
FROM Employee e
INNER JOIN (
    SELECT DeptID, AVG(Salary) AS AvgDeptSalary 
    FROM Employee 
    GROUP BY DeptID
) AS dept_avg ON e.DeptID = dept_avg.DeptID
WHERE e.Salary > dept_avg.AvgDeptSalary;
                
            

Exam Strategy – SQL (2026 Boards)

Most repeated questions: Table creation with constraints, SELECT with JOIN/GROUP BY/HAVING, second highest salary, subqueries
Mark distribution: 10–15 marks from SQL alone (2–3 questions)
Tip: Always write exact syntax, use proper capitalization (SELECT, FROM, WHERE), mention table/column names clearly
Time: 15–18 minutes for 10–12 mark SQL question
Practice: Solve last 5 years papers + sample papers 2025–26, focus on output-based & error-finding questions

This guide covers the most important SQL topics & code examples for Class 12 Computer Science.