How to Pass the Amazon SQL Interview (A Practical Guide)

If you are preparing for a Business Intelligence, Data Analyst, Data Engineer, or Data Scientist position at Amazon, you likely know that SQL is a critical component of the hiring process. However, Amazon's expectations go beyond simply testing your syntax. They want to assess your ability to think in sets, write clean queries under pressure, and reason about data in ways that matter to the business. Here's a practical guide on how to prepare based on what the interview actually rewards.

The Amazon SQL rounds typically occur in two formats: a technical screen through a shared coding tool or a whiteboarding case-study during the main interview loop. In either scenario, the interviewer is looking for specific indicators. First and foremost, correctness is always more important than speed. A functioning query will always outperform a clever one that fails.

Communication is also of utmost importance. Before you even start writing code, you'll be expected to articulate your logic out loud. You'll often be given a vague request, such as identifying the best customers. It is essential to define what "best" means verbally before you begin coding.

Common Table Expressions (CTEs) are highly preferred by interviewers due to their readability and ease of explanation. Avoid nested subqueries whenever possible and opt for well-structured queries with clear CTEs. Understanding date and time manipulation is crucial for cohort analysis, retention windows, and rolling averages, which are frequently seen in Amazon interviews given their retail and logistics emphasis.

You'll need to practice using DATE_TRUNC, finding date differences, and writing rolling window aggregations. Always be prepared to handle nulls and duplicates in the data, as these are common sources of confusing results.

To effectively prepare for the Amazon SQL interview, focus on mastering joins, window functions, aggregations, and group logic. Practice on messy datasets with duplicates and nulls to ensure these scenarios become second nature. Time yourself to simulate the real interview environment, aiming to write a correct, readable query in under 15 minutes.

Narrate your thought process out loud, even when alone, as this skill is essential during the interview. Lastly, be aware of common mistakes like jumping straight into code without clarifying the metric, writing overly complex queries, ignoring data issues, and failing to check the context of aggregate functions. Mastering these skills will make you well-prepared for the Amazon SQL interview.