SQL interviews often include complex and tricky questions designed to assess your problem-solving skills, creativity, and ability to write efficient queries. If you’re preparing for an upcoming SQL interview, tackling these types of questions can significantly enhance your confidence and performance.
Below, we’ve compiled a list of some challenging SQL questions with Solutions, covering a variety of scenarios that test your command of database operations:
Understanding Arithmetic Operators in Python
Advanced SQL Interview Questions
Question 1: How can you find the second-highest salary in a table without using the LIMIT or TOP keyword?
Answer 1: SELECT MAX(salary) FROM table_name WHERE salary < (SELECT MAX(salary) FROM table_name);
Question 2: Write a query to identify employees who earn more than their managers.
Answer 2: SELECT e1.* FROM employees e1 JOIN employees e2 ON e1.manager_id = e2.id WHERE e1.salary > e2.salary;
Question 3: Devise a query to detect duplicate rows in a table without utilizing GROUP BY.
Answer 3: SELECT column1, column2 FROM table_name WHERE (column1, column2) IN (SELECT column1, column2 FROM table_name GROUP BY column1, column2 HAVING COUNT(*) > 1);
Question 4: How would you retrieve the top 10% of earners from a table?
Answer 4: SELECT * FROM (SELECT *, NTILE(10) OVER (ORDER BY salary DESC) AS percentile FROM table_name) subquery WHERE percentile = 1;
Question 5: Write a query to calculate the cumulative sum of values in a column.
Answer 5: SELECT column, SUM(column) OVER (ORDER BY id) AS cumulative_sum FROM table_name;
Question 6: Find all employees who have never taken any leave.
Answer 6: SELECT * FROM employees WHERE id NOT IN (SELECT employee_id FROM leaves);
Question 7: Create a query to compute the difference between the current row and the next row in a dataset.
Answer 7: SELECT *, column – LEAD(column) OVER (ORDER BY id) AS difference FROM table_name;
Question 8: Identify all departments that have more than one employee.
Answer 8: SELECT department FROM employees GROUP BY department HAVING COUNT(*) > 1;
Question 9: Retrieve the maximum value of a column for each group without using GROUP BY.
Answer 9: SELECT DISTINCT ON (group_column) group_column, column FROM table_name ORDER BY group_column, column DESC;
Question 10: Find all employees who have taken more than three leaves in a single month.
Answer 10: SELECT employee_id FROM leaves GROUP BY employee_id, MONTH(leave_date) HAVING COUNT(*) > 3;
