Duplicate Emails
A easy-tier problem at 72% community acceptance, tagged with Database. Reported in interviews at EPAM Systems and 2 others.
Duplicate Emails is an easy database problem that shows up at Google, EPAM Systems, and TCS. You're looking at a 72% acceptance rate, which sounds forgiving until you realize most candidates who fail it are rusty on SQL fundamentals or don't know how to structure a GROUP BY with HAVING. This is the kind of problem that feels trivial on paper but trips up engineers who haven't written SQL in months. If this hits your live assessment and your brain goes blank on the syntax, StealthCoder surfaces a working query in seconds, invisible to the proctor.
Companies that ask "Duplicate Emails"
Duplicate Emails is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trap here is thinking you need a join or a subquery when the real solution is GROUP BY with a HAVING clause to filter groups with count greater than 1. Most candidates either write inefficient nested selects or struggle with the aggregate function syntax. The obvious wrong approach is trying to self-join the table and then deduplicate manually. The pattern is straightforward once you see it: group by email, count occurrences, filter where count is greater than one, and return the email. Window functions work too but add unnecessary complexity. This is a check-the-fundamentals problem. If you haven't written SQL in a while, StealthCoder is the hedge for the 30 seconds you'd otherwise waste second-guessing yourself on GROUP BY syntax.
Pattern tags
You know the problem.
Make sure you actually pass it.
Duplicate Emails recycles across companies for a reason. It's easy-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Duplicate Emails interview FAQ
Is Duplicate Emails still asked at Google and other major companies?+
Yes. It's reported by Google, EPAM Systems, and TCS. It's a database fundamentals check, not a trick question. Interviewers use it to verify you can write clean SQL without overthinking. The 72% acceptance rate is high, but that includes people who prepped. Don't assume it's a gimme.
What's the core trick everyone misses?+
Using GROUP BY with HAVING count(*) > 1 instead of trying to self-join or use a subquery. Candidates often overcomplicate it by writing nested queries or window functions. The pattern is group, aggregate, filter. That's it. Once you see it once, it sticks.
How does this relate to database topics I should know?+
This is pure aggregation and filtering. You need solid GROUP BY syntax, aggregate functions like COUNT, and the HAVING clause to filter grouped results. These three pieces show up in every database round. Master them here and you're ready for harder grouping problems.
Is window functions the better approach?+
No. Window functions work but they're overkill and slower. GROUP BY with HAVING is the expected answer. Window functions signal over-engineering. Keep it simple. Interviewers respect efficient, readable SQL over clever tricks.
What if I blank on the syntax during the live assessment?+
That's why you prep. Write out GROUP BY and HAVING five times before the OA. But if you hit a wall and can't remember aggregate function syntax, StealthCoder runs invisibly and shows you a clean, working solution so you can paste and move on.
Want the actual problem statement? View "Duplicate Emails" on LeetCode →