SQL Queries and Database Interview Questions and Answers for Coding Rounds

Preparing for SQL coding challenges is essential for cracking technical interviews, especially when companies evaluate candidates on real-world querying skills. Most recruiters focus on practical tasks rather than theoretical concepts, which is why practicing database interview questions and answers can significantly improve your confidence during coding rounds.

Coding interviews often include SQL problem-solving that tests your logical thinking, understanding of relational databases, and ability to write optimized queries. To excel in these tests, candidates must go beyond basic SELECT statements and master joins, subqueries, window functions, indexing concepts, and performance optimization.

Practicing database interview questions and answers that mimic real business scenarios helps you strengthen both accuracy and speed—two key factors evaluated during live assessments.

Below is a comprehensive set of SQL query-based questions, detailed explanations, and efficient solutions to help you prepare effectively for coding rounds.

1. Write a query to find the second highest salary from the Employees table.

This is one of the most frequently asked questions in SQL interviews.

Solution:

SELECT MAX(Salary) AS SecondHighestSalary
FROM Employees
WHERE Salary < (SELECT MAX(Salary) FROM Employees);

This method avoids using LIMIT or TOP and works across major SQL databases.

2. Retrieve the number of employees in each department.

This question tests knowledge of grouping and aggregations.Solution:

SELECT Department, COUNT(*) AS EmployeeCount
FROM Employees
GROUP BY Department;

3. Find employees who earn more than the average salary.

Shows your ability to work with subqueries.Solution:

SELECT *
FROM Employees
WHERE Salary > (SELECT AVG(Salary) FROM Employees);

4. Write a query to display duplicate email IDs from a Users table.

Often used to test your understanding of GROUP BY and HAVING.

Solution:

SELECT Email, COUNT(*) AS DuplicateCount
FROM Users
GROUP BY Email
HAVING COUNT(*) > 1;

5. Fetch the top 3 highest salaries from a Salary table.

Solution (MySQL/PostgreSQL):

SELECT Salary
FROM Employees
ORDER BY Salary DESC
LIMIT 3;

Solution (SQL Server):

SELECT TOP 3 Salary
FROM Employees
ORDER BY Salary DESC;

6. Retrieve all employees who have not submitted any project.

Testing LEFT JOIN usage.Solution:

SELECT e.EmployeeID, e.Name
FROM Employees e
LEFT JOIN Projects p
ON e.EmployeeID = p.EmployeeID
WHERE p.EmployeeID IS NULL;

7. Display the highest salary for each department.

Evaluates your grouping and aggregation skills.

Solution:

SELECT Department, MAX(Salary) AS HighestSalary
FROM Employees
GROUP BY Department;

8. Write a query to rank employees by their salary.

Tests window functions.Solution:

SELECT 
    Name,
    Salary,
    RANK() OVER (ORDER BY Salary DESC) AS SalaryRank
FROM Employees;

9. Fetch employees whose names start with ‘A’.

Tests pattern matching.

Solution:

SELECT *
FROM Employees
WHERE Name LIKE 'A%';

10. Delete duplicate rows but keep only the first occurrence.

Intermediate-to-advanced skill test.

Solution (using ROW_NUMBER):

WITH RankedData AS (
    SELECT *, ROW_NUMBER() OVER (
        PARTITION BY Name, Salary, Department 
        ORDER BY EmployeeID
    ) AS row_num
    FROM Employees
)
DELETE FROM RankedData
WHERE row_num > 1;

Final Thoughts

Mastering SQL queries is crucial for standing out in coding rounds, especially when companies assess your problem-solving ability under time pressure. By practicing real-world tasks and exploring advanced concepts like joins, subqueries, CTEs, and window functions, you prepare yourself for both beginner-level and challenging scenarios. Make sure you regularly revise database interview questions and answers to improve consistency and accuracy before stepping into your next technical interview.