SQL (Structured Query Language) is one of the most common topics asked in any technical interview — whether you’re a fresher or an experienced professional.
In this post, we’ll go through important SQL program-based questions that are often asked in interviews, along with easy-to-understand answers and examples.

Let’s begin 👇

---

1. Write an SQL query to display the second highest salary from an Employee table.

Table Name: Employee

Columns: id, name, salary

Query:

SELECT MAX(salary) AS Second_Highest_Salary
FROM Employee
WHERE salary < (SELECT MAX(salary) FROM Employee);

Explanation:

• First, we find the maximum salary using a subquery.
• Then we select the maximum salary that is less than that maximum — which gives us the second highest salary.
• This is one of the most popular interview questions.

✅ Tip: You can also use LIMIT or TOP depending on your database (MySQL or SQL Server).

---

2. Write an SQL query to fetch duplicate records from a table.

Table: Students

Columns: id, name, email

Query:

SELECT name, COUNT(*)
FROM Students
GROUP BY name
HAVING COUNT(*) > 1;

Explanation:

• GROUP BY groups rows with the same name.
• HAVING COUNT(*) > 1 filters only those names that appear more than once.
  This helps in finding duplicates easily.

---

3. Write an SQL query to fetch the first three highest salaries.

Query (MySQL):

SELECT DISTINCT salary
FROM Employee
ORDER BY salary DESC
LIMIT 3;

Explanation:

• The ORDER BY salary DESC sorts salaries in descending order.
• LIMIT 3 returns the top 3 salaries.
• If you want to find the third highest salary only, use LIMIT 2,1.

---

4. Write an SQL query to count total employees in each department.

Table: Employee

Columns: id, name, department, salary

Query:

SELECT department, COUNT(*) AS Total_Employees
FROM Employee
GROUP BY department;

Explanation:

• GROUP BY is used to group data by department.
• COUNT(*) counts how many employees are there in each department.

---

5. Write an SQL query to find employees whose name starts with ‘A’.

Query:

SELECT * 
FROM Employee
WHERE name LIKE 'A%';

Explanation:

• The LIKE operator is used for pattern matching.
• 'A%' means any name starting with letter ‘A’.
• 'A_' would mean names starting with A and having only one more character after it.

---

6. Write an SQL query to get the current date.

Query (MySQL):

SELECT CURDATE();

Query (SQL Server):

SELECT GETDATE();

Explanation:

This is a simple query but often asked to check your basic command of SQL functions.

---

7. Write an SQL query to show employees who earn more than the average salary.

Query:

SELECT name, salary
FROM Employee
WHERE salary > (SELECT AVG(salary) FROM Employee);

Explanation:

• The subquery (SELECT AVG(salary) FROM Employee) gives the average salary.
• The main query then selects those who earn above average.

---

8. Write an SQL query to find the nth highest salary.

For MySQL:

SELECT DISTINCT salary
FROM Employee e1
WHERE (n-1) = (
    SELECT COUNT(DISTINCT salary)
    FROM Employee e2
    WHERE e2.salary > e1.salary
);

Explanation:

• Replace n with any number (like 3 for third highest).
• It compares how many salaries are greater than the current one and selects the required rank.

---

9. Write an SQL query to join two tables (Employee and Department).

Table 1: Employee(id, name, dept_id)

Table 2: Department(dept_id, dept_name)

Query:

SELECT e.name, d.dept_name
FROM Employee e
INNER JOIN Department d
ON e.dept_id = d.dept_id;

Explanation:

• INNER JOIN returns only the matching records from both tables.
• It helps combine related data from multiple tables.

---

10. Write an SQL query to remove duplicate records from a table.

Query (Using ROW_NUMBER):

DELETE FROM Employee
WHERE id NOT IN (
  SELECT MIN(id)
  FROM Employee
  GROUP BY name, salary, department
);

Explanation:

• We keep only the record with the smallest id for each unique combination.
• The rest are deleted, effectively removing duplicates.

---

11. Write an SQL query to find employees who do not belong to any department.

Query:

SELECT name
FROM Employee
WHERE dept_id IS NULL;

Explanation:

• IS NULL is used to find missing or empty values.
• Common question to test your knowledge of null handling.

---

12. Write an SQL query to get department names and their total salary expense.

Query:

SELECT department, SUM(salary) AS Total_Salary
FROM Employee
GROUP BY department;

Explanation:

• The SUM() function adds up salaries of each department.
• Useful for finance or reporting type questions.

---

13. Write an SQL query to display employees who joined in the last 3 months.

Query (MySQL):

SELECT * 
FROM Employee
WHERE joining_date >= DATE_SUB(CURDATE(), INTERVAL 3 MONTH);

Explanation:

• DATE_SUB() subtracts time from the current date.
• It fetches employees who joined recently — very common real-world query.

---

14. Write an SQL query to find employees whose salary is between 30,000 and 60,000.

Query:

SELECT * 
FROM Employee
WHERE salary BETWEEN 30000 AND 60000;

Explanation:

• BETWEEN is an inclusive range — includes both boundary values.

---

15. Write an SQL query to fetch top 5 records from a table.

Query (MySQL):

SELECT * 
FROM Employee
LIMIT 5;

Query (SQL Server):

SELECT TOP 5 * 
FROM Employee;

Explanation:

• The syntax changes slightly based on the database.
• This is used for previewing or testing small datasets.

---

16. Write an SQL query to find the total number of employees who joined each year.

Query:

SELECT YEAR(joining_date) AS Join_Year, COUNT(*) AS Total_Employees
FROM Employee
GROUP BY YEAR(joining_date)
ORDER BY Join_Year;

Explanation:

• The YEAR() function extracts the year from the date.
• This helps understand hiring trends.

---

17. Write an SQL query to display employees along with their manager names.

Table: Employee(id, name, manager_id)

Query:

SELECT e.name AS Employee, m.name AS Manager
FROM Employee e
LEFT JOIN Employee m
ON e.manager_id = m.id;

Explanation:

• The self-join helps show hierarchical relationships.
• LEFT JOIN ensures even employees without managers appear.

---

18. Write an SQL query to count male and female employees.

Query:

SELECT gender, COUNT(*) AS Total
FROM Employee
GROUP BY gender;

Explanation:

• Simple GROUP BY example that also checks your understanding of category-based data.

---

19. Write an SQL query to list employees with the same salary.

Query:

SELECT salary, COUNT(*) 
FROM Employee
GROUP BY salary
HAVING COUNT(*) > 1;

Explanation:

• Similar to duplicate check — it shows which salaries appear more than once.

---

20. Write an SQL query to rank employees based on salary.

Query (Using RANK()):

SELECT name, salary, 
       RANK() OVER (ORDER BY salary DESC) AS Rank_Position
FROM Employee;

Explanation:

• RANK() gives each employee a rank based on their salary.
• If two employees have the same salary, they share the same rank.

---

✅ Final Tips for SQL Program Interviews

• Always understand the logic behind each query — don’t just memorize.
• Practice queries on real sample data.
• Be ready to explain your thought process to the interviewer.
• Know basic SQL functions like MAX(), MIN(), AVG(), COUNT(), and SUM().
• Learn Joins, Subqueries, and Window Functions — they’re interview favorites.

---

Conclusion

These SQL program-based interview questions cover everything from basic to advanced levels. If you practice these well, you’ll feel confident in any SQL interview.
SQL is not just about queries — it’s about logic and problem-solving. So focus on understanding the “why” behind every question.

Glimsy.in – Learn Smart, Grow Confident.

---