SQL Interview Questions You Need to Know (With Solutions)

SQL remains one of the most in-demand skills in tech. Whether you’re applying for a data analyst, backend developer, or business intelligence role, you’ll likely face SQL questions during the interview process. Employers want to know if you can query data effectively, optimize performance, and solve real-world problems.

In this article, we’ll cover essential SQL interview questions — along with solutions and explanations — to help you prepare with confidence.

1. Select All Records from a Table

Question:
Write a query to fetch all columns from a table named employees.

SELECT * 
FROM employees;

Explanation:
A basic query, but often the starting point in interviews. It checks whether you understand SELECT and table structures.

2. Filter Records with Conditions

Question:
Fetch the first and last names of employees who work in the “Sales” department.

SELECT first_name, last_name 
FROM employees
WHERE department = 'Sales';

Key Point:
WHERE is used for filtering records based on conditions.

3. Aggregate Functions

Question:
Find the average salary of employees in the “IT” department.

SELECT AVG(salary) AS avg_salary
FROM employees
WHERE department = 'IT';

Why It’s Asked:
Tests understanding of aggregate functions like SUM(), AVG(), MAX(), and MIN().

4. Grouping and Counting

Question:
Show the number of employees in each department.

SELECT department, COUNT(*) AS employee_count
FROM employees
GROUP BY department;

Explanation:
The GROUP BY clause is crucial for data summarization, often paired with aggregate functions.

5. Joins

Question:
Retrieve employee names along with their manager’s name. Assume tables employees(emp_id, name, manager_id) and managers(manager_id, name).

SELECT e.name AS employee_name, m.name AS manager_name
FROM employees e
JOIN managers m 
  ON e.manager_id = m.manager_id;

Key Concept:
Understanding INNER JOIN is essential for combining related tables.

6. Subqueries

Question:
Find employees whose salary is above the company’s average.

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

Explanation:
Subqueries test your ability to nest queries and use the results in conditions.

7. Window Functions (Advanced)

Question:
Rank employees by salary within each department.

SELECT 
  name, 
  department, 
  salary,
  RANK() OVER (PARTITION BY department ORDER BY salary DESC) AS dept_rank
FROM employees;

Why It Matters:
Window functions are increasingly common in modern SQL interviews, especially for analytics roles.

Pro Tips for SQL Interviews

Practice on Real Data: Use free datasets like Chinook or Sakila to simulate real queries.
Explain Your Thought Process: Don’t just give the query; explain why you wrote it that way.
Optimize: Be prepared to discuss indexes and performance improvements.
Stay Calm: Interviewers value structured problem-solving, not just memorized queries.

Final Thoughts

Mastering SQL interview questions is less about memorizing queries and more about understanding concepts. Practice writing queries daily, build small projects using databases, and challenge yourself with progressively complex problems.

With consistent practice, you’ll not only ace your interviews but also develop skills that directly transfer to real-world data work.