amazon interview questions on sql

Art Scpae

3 min read

·

25-09-2024

117

0

Share

Cracking the Code: Amazon's SQL Interview Questions

Landing a job at Amazon is a dream for many tech professionals. Their rigorous interview process is known to test candidates on various skills, including SQL. While the specific questions may vary, the underlying themes remain consistent: understanding data manipulation, optimization, and analytical thinking.

This article dives into some common SQL interview questions asked at Amazon, providing insights into the types of problems you might encounter and offering practical tips to ace them.

1. "Write a SQL query to find the top 5 products with the highest sales in the last quarter."

This question tests your ability to filter data, aggregate results, and apply ranking functions. Here's a possible solution:

SELECT product_name, SUM(quantity * price) AS total_sales
FROM sales
WHERE order_date >= DATE_SUB(CURDATE(), INTERVAL 3 MONTH) 
GROUP BY product_name
ORDER BY total_sales DESC
LIMIT 5;

Explanation:

• DATE_SUB(CURDATE(), INTERVAL 3 MONTH): This calculates the date three months prior to the current date, effectively defining the last quarter.
• GROUP BY product_name: Aggregates sales data by product name.
• ORDER BY total_sales DESC: Sorts products in descending order based on their total sales.
• LIMIT 5: Returns the top 5 products.

2. "Given two tables, 'Customers' and 'Orders', write a query to find customers who haven't placed any orders in the last year."

This question emphasizes joins, date calculations, and subqueries.

SELECT c.customer_id, c.customer_name
FROM Customers c
LEFT JOIN Orders o ON c.customer_id = o.customer_id
WHERE o.order_date < DATE_SUB(CURDATE(), INTERVAL 1 YEAR)
GROUP BY c.customer_id, c.customer_name
HAVING COUNT(DISTINCT o.order_id) = 0;

Explanation:

• LEFT JOIN: Combines the Customers and Orders tables, keeping all customers even if they have no orders.
• WHERE o.order_date < DATE_SUB(CURDATE(), INTERVAL 1 YEAR): Filters orders to only include those placed before the last year.
• GROUP BY c.customer_id, c.customer_name: Groups the results by customer.
• HAVING COUNT(DISTINCT o.order_id) = 0: Identifies customers with no orders in the last year.

3. "Explain the difference between an INNER JOIN and a LEFT JOIN."

This question assesses your understanding of fundamental join types.

Answer:

• INNER JOIN: Returns rows only when there's a match in both tables.
• LEFT JOIN: Returns all rows from the left table, even if there are no matching rows in the right table. Null values are returned for the right table's columns if there's no match.

4. "How would you optimize a slow SQL query?"

This question tests your practical knowledge of query optimization.

Answer:

• Use appropriate indexes: Indexes speed up data retrieval by allowing the database to quickly locate specific records.
• Minimize data returned: Use SELECT clauses to retrieve only the necessary columns.
• Avoid unnecessary subqueries: Optimize subqueries or replace them with joins where possible.
• Use efficient data types: Choose appropriate data types to minimize storage and processing requirements.
• Analyze query plans: Use tools to visualize query plans and identify bottlenecks.

Additional Tips:

• Practice regularly: Use online platforms like LeetCode or HackerRank to hone your SQL skills.
• Review Amazon's Leadership Principles: Understand how your skills align with Amazon's principles.
• Be confident and articulate: Clearly explain your thought process and reasoning behind your solutions.

Remember: Amazon is looking for individuals who can solve complex data problems efficiently and effectively. By understanding the concepts behind SQL and practicing with relevant questions, you can increase your chances of succeeding in your interview.

Note: This article was created using information from various sources including Github and Stack Overflow. Always double-check information for accuracy and reliability.

Further Research:

• SQL Interview Questions for Amazon
• LeetCode SQL Problems
• HackerRank SQL Challenges