SQL Question Bank

Do you need help finding SQL questions on the internet? Searching ends here.

I've compiled all the SQL questions I found on social media, such as LinkedIn, YouTube, Instagram, and Telegram. Let's dive into the database world.

Top Interview Questions SQL

Q1: Explain the difference between RANK(), DENSE_RANK(), and ROW_NUMBER() functions using example.

Q2 – Q4 use Table: employee (EmpID, ManagerID, JoinDate, Dept, Salary)

Q2: Find the nth highest salary from the Employee table.

Q3: You have an employee table with employee ID and manager ID. Find all employees under a specific manager, including their subordinates at any level.

Q4: Write a query to find the cumulative salary of employees department-wise, who have joined the company in the last 30 days.

Q5: Find the top 2 customers with the highest order amount for each product category, handling ties appropriately. Table: Customer (CustomerID, ProductCategory, OrderAmount)

[1] Top N Analysis: Find top N products by sales, top N employees by salaries, or top N items within each category.

[2] Year-Over-Year Growth: Calculate YOY growth, products with higher sales than the previous month, or category-wise growth.

[3] Running Totals: Track running sales over months, rolling N months' sales, especially within categories.

[4] Pivot Operations: Transform rows to columns, such as displaying year-wise sales for each category in separate columns.

[5] Join Analysis: Count the records resulting from different types of joins.

1. How do window functions work in SQL, and when would you use them?

2. What is the purpose of indexing in SQL? How do you decide when to create an index?

3. Can you explain the differences between UNION and UNION ALL?

4. How do you write a SQL query to find the second highest salary in a table?

5. What are CTEs (Common Table Expressions) and their benefits?

1- Find the second-highest salary in a department. You may need to use the ROW_NUMBER() or DENSE_RANK() function to solve this.

2- Write a SQL query to return the total number of transactions per user for each day. This could involve using GROUP BY and COUNT() functions. This is common in data aggregation tasks.

3- Create a query that selects projects with the highest budget-per-employee ratio from two related tables (projects and employees). This tests your ability to handle complex joins and aggregations.

1. Find the second-highest salary in a table without using LIMIT or TOP.

2. Write a SQL query to find all employees who earn more than their managers.

3. Find the duplicate rows in a table without using GROUP BY.

4. Write a SQL query to find the top 10% of earners in a table.

5. Find the cumulative sum of a column in a table.

6. Write a SQL query to find all employees who have never taken a leave.

7. Find the difference between the current row and the next row in a table.

8. Write a SQL query to find all departments with more than one employee.

9. Find the maximum value of a column for each group without using GROUP BY.

10. Write a SQL query to find all employees who have taken more than 3 leaves in a month.

These questions are designed to test your SQL skills, including your ability to write efficient queries, think creatively, and solve complex problems.

Here are the answers to these questions:

1. SELECT MAX(salary) FROM table WHERE salary NOT IN (SELECT MAX(salary) FROM table)

2. SELECT e1.* FROM employees e1 JOIN employees e2 ON e1.manager_id = (link unavailable) WHERE e1.salary > e2.salary

3. SELECT * FROM table WHERE rowid IN (SELECT rowid FROM table GROUP BY column HAVING COUNT(*) > 1)

4. SELECT * FROM table WHERE salary > (SELECT PERCENTILE_CONT(0.9) WITHIN GROUP (ORDER BY salary) FROM table)

5. SELECT column, SUM(column) OVER (ORDER BY rowid) FROM table

6. SELECT * FROM employees WHERE id NOT IN (SELECT employee_id FROM leaves)

7. SELECT *, column - LEAD(column) OVER (ORDER BY rowid) FROM table

8. SELECT department FROM employees GROUP BY department HAVING COUNT(*) > 1

9. SELECT MAX(column) FROM table WHERE column NOT IN (SELECT MAX(column) FROM table GROUP BY group_column)

Source: Check out my LinkedIn profile... /RakeshMen