Uploaded June 2026 | Updated September 2026, 4 hours ago

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Struggling with advanced SQL interview questions for data roles? You’re not alone. In this video, we break down a real Amazon SQL interview question: How to calculate the Day 1 retention rate for video game players.

Most data analysts and engineers get this question completely wrong. It’s not because the SQL code itself is overly complicated — it’s because they fall into sneaky optimization traps and metric definition pitfalls that instantly signal a lack of seniority to FAANG interviewers.

📝 Key Takeaways for Your Interview
To pass a FAANG interview, writing code isn't enough — you have to explain the why. Interviewers grade you on three pillars: defining the metric correctly, implementing the proper join/denominator logic, and interpreting the real-world business meaning.

1. The Base CTE: Always compute the user's earliest login first—it's the foundation of almost every retention query.
2. The Left Join Rule: Always use a `LEFT JOIN` when looking for day-after activity so users who didn't return stay in your denominator.
3. The Seniority Phrase: Mentioning how to filter out users who haven't reached the maturity threshold (avoiding survivorship bias) signals senior-level data expertise without you even having to code it unprompted.

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Ready to try it yourself? Practice coding and interpretation with this retention interview question 👉 platform.stratascratch.com/coding/2090-first-day-retention-rate?code_type=1&utm_source=youtube&utm_medium=click&utm_campaign=YT+wrong+retention+in+sql

📖 Full article: stratascratch.com/blog/retention-in-sql-how-to-calculate-user-and-cohort-retention?utm_source=youtube&utm_medium=click&utm_campaign=YT+wrong+retention+in+sql

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📅 Video Timeline:

0:00 - The Amazon SQL Interview Question
0:20 - The Retention Formula & Churn Pitfalls
1:05 - Step 1: Building the Base CTE (Earliest Login)
1:23 - Step 2: The Critical Left Join (Avoiding Inflated Metrics)
1:45 - How to Avoid Survivorship Bias (The Day 30 Problem)
2:20 - Upgrading to Cohort Retention (What PMs Actually Want)
3:00 - The 3 Things Interviewers Look For
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About StrataScratch:

StrataScratch (platform.stratascratch.com/coding?code_type=2&page_size=100&utm_source=youtube&utm_medium=click&utm_campaign=YT+wrong+retention+in+sql) is a platform that allows you to practice real data science interview questions. There are over 1000+ interview questions that cover coding (SQL and Python), statistics, probability, product sense, and business cases.

So, if you want more interview practice with real data science interview questions, visit platform.stratascratch.com/coding?code_type=2&page_size=100&utm_source=youtube&utm_medium=click&utm_campaign=YT+wrong+retention+in+sql. All questions are free and you can even execute SQL and Python code in the IDE. Still, if you want to check out the solutions from other users or from the StrataScratch team, you can use ss15 for a 15% discount on the premium plans.

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📧 Contact Us: Got questions or feedback? Drop them in the comments or email us at team@stratascratch.com.
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