SQL is one of the most important skills evaluated during technical interviews for roles such as SQL Developer, Data Analyst, Database Administrator, Software Developer, and Business Intelligence Analyst. Interviewers often ask candidates to write SQL queries to check their understanding of databases, filtering, joins, aggregate functions, and data manipulation.
Learning through an SQL Course in Telugu can help beginners understand these concepts step by step and practise queries with practical examples. Instead of memorising answers, candidates should understand how each query works and when to use it.
Why Are SQL Queries Important in IT Interviews?
Companies use databases to store and manage information such as customer details, employee records, orders, and transactions. SQL helps professionals retrieve, update, and analyse this information.
During interviews, candidates may receive a sample table and be asked to solve a problem using SQL. Regular query practice improves logical thinking, problem-solving skills, and confidence.
Sample Employee Table
Consider an employee table with the following columns:
- emp_id – Employee ID
- emp_name – Employee name
- department – Department name
- salary – Employee salary
- city – Employee location
Top 30 SQL Queries for IT Interviews
Basic SQL Queries
1. Retrieve all employee records
SELECT * FROM employees;
2. Display only employee names and salaries
SELECT emp_name, salary FROM employees;
3. Find employees earning more than 40,000
SELECT * FROM employees
WHERE salary > 40000;
4. Display employees from the IT department
SELECT * FROM employees
WHERE department = 'IT';
5. Sort employees by salary in descending order
SELECT * FROM employees
ORDER BY salary DESC;
6. Find employees from Hyderabad
SELECT * FROM employees
WHERE city = 'Hyderabad';
7. Retrieve the first five employee records
SELECT * FROM employees
LIMIT 5;
8. Find unique department names
SELECT DISTINCT department FROM employees;
9. Search employee names beginning with A
SELECT * FROM employees
WHERE emp_name LIKE 'A%';
10. Find employees whose salary is between 30,000 and 60,000
SELECT * FROM employees
WHERE salary BETWEEN 30000 AND 60000;
Aggregate Function Queries
11. Calculate the total number of employees
SELECT COUNT(*) FROM employees;
12. Find the highest salary
SELECT MAX(salary) FROM employees;
13. Find the lowest salary
SELECT MIN(salary) FROM employees;
14. Calculate the average salary
SELECT AVG(salary) FROM employees;
15. Calculate the total salary paid to employees
SELECT SUM(salary) FROM employees;
16. Count employees in each department
SELECT department, COUNT(*)
FROM employees
GROUP BY department;
17. Find departments with more than five employees
SELECT department, COUNT(*)
FROM employees
GROUP BY department
HAVING COUNT(*) > 5;
Joins and Subqueries
18. Display employee names with department details
SELECT e.emp_name, d.department_name
FROM employees e
INNER JOIN departments d
ON e.department_id = d.department_id;
19. Retrieve all employees, including those without matching department records
SELECT e.emp_name, d.department_name
FROM employees e
LEFT JOIN departments d
ON e.department_id = d.department_id;
20. Find employees earning more than the average salary
SELECT * FROM employees
WHERE salary > (SELECT AVG(salary) FROM employees);
21. Find the second-highest salary
SELECT MAX(salary)
FROM employees
WHERE salary < (SELECT MAX(salary) FROM employees);
22. Find employees who receive the highest salary
SELECT * FROM employees
WHERE salary = (SELECT MAX(salary) FROM employees);
23. Find employees who belong to the same department as a given employee
SELECT * FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
WHERE emp_id = 101
);
Advanced SQL Queries
24. Identify duplicate employee names
SELECT emp_name, COUNT(*)
FROM employees
GROUP BY emp_name
HAVING COUNT(*) > 1;
25. Find the third-highest distinct salary
SELECT DISTINCT salary
FROM employees
ORDER BY salary DESC
LIMIT 1 OFFSET 2;
26. Assign a ranking based on salary
SELECT emp_name, salary,
RANK() OVER (ORDER BY salary DESC) AS salary_rank
FROM employees;
27. Calculate a running salary total
SELECT emp_name, salary,
SUM(salary) OVER (ORDER BY emp_id) AS running_total
FROM employees;
28. Find the highest-paid employee in each department
SELECT emp_name, department_id, salary
FROM (
SELECT emp_name, department_id, salary,
ROW_NUMBER() OVER (
PARTITION BY department_id
ORDER BY salary DESC
) AS rn
FROM employees
) ranked
WHERE rn = 1;
29. Find employees with missing city information
SELECT * FROM employees
WHERE city IS NULL;
30. Replace missing city values with a default value in the output
SELECT emp_name,
COALESCE(city, 'Not Provided') AS city
FROM employees;
Note: These examples use common SQL syntax. A few features, such as LIMIT, may differ across database systems.
How to Practise These Queries Effectively
Start with basic SELECT statements and gradually move towards joins, subqueries, and window functions. Create sample tables and insert your own records to understand how the output changes.
Practise explaining your approach instead of only writing the final query. This demonstrates your understanding during technical interviews.
Frequently Asked Questions
1. Is SQL important for freshers?
Yes. SQL is useful for freshers applying for data analyst, software development, testing, and database-related positions.
2. How many SQL queries should I practise daily?
Practising 10–15 queries daily with proper understanding can help build consistency.
3. Which SQL topics are important for interviews?
Joins, subqueries, aggregate functions, constraints, grouping, filtering, and window functions are important topics.
4. Can I learn SQL without programming experience?
Yes. Beginners can start with database basics and gradually learn query writing without previous programming knowledge.
5. How can I improve my SQL interview performance?
Solve practical problems, understand query logic, practise sample datasets, and explain your answers clearly.
Conclusion
SQL interview preparation requires more than memorising query syntax. Candidates should understand how to retrieve, filter, combine, and analyse data using different SQL commands. Practising these 30 commonly used queries can strengthen your technical foundation. An SQL Course in Telugu can also make complex database concepts easier to understand through structured lessons and hands-on exercises.
