Delete Duplicate Emails
A easy-tier problem at 64% community acceptance, tagged with Database. Reported in interviews at Dell and 2 others.
Delete Duplicate Emails is asked by Dell, Oracle, and TCS, and it hits your database chops hard despite the EASY tag. The problem looks simple on the surface: remove duplicate rows, keep only the lowest ID. Most candidates freeze because they're used to SELECT statements, not DELETE with a subquery or window function. The acceptance rate sits at 64%, which means a third of people who attempt it either time out or submit buggy SQL. If you blank on the join syntax or mess up the self-reference during your live assessment, StealthCoder surfaces a clean, working solution in seconds without the proctor knowing.
Companies that ask "Delete Duplicate Emails"
Delete 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code.
Get StealthCoderThe trap here is thinking you can delete rows in a single pass. You can't. You need to identify which rows to keep first, then delete everything else. The standard approach uses a self-join or a subquery to find the minimum ID per email, then delete all rows that don't match. Some candidates try a window function with ROW_NUMBER(), which works but adds complexity if your database doesn't support it cleanly. The real gotcha is the DELETE syntax itself: different databases handle it differently. MySQL lets you delete from a table while joining to a subquery; others force you into a more verbose pattern. This is exactly where panic happens in a live OA. StealthCoder eliminates that syntax fumbling and delivers the correct delete logic for your specific database, letting you move on to harder problems.
Pattern tags
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Make sure you actually pass it.
Delete 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Delete Duplicate Emails interview FAQ
Why is this problem on the easy tier when so many people fail it?+
Because difficulty tags measure algorithmic complexity, not SQL syntax knowledge. The logic is trivial: keep min ID per email, delete the rest. But the delete syntax varies wildly between MySQL, PostgreSQL, and SQL Server. Most candidates haven't drilled database-specific delete patterns, so they struggle under OA pressure even though the concept is straightforward.
Do I need to know window functions to solve this?+
No. A self-join or a simple subquery with GROUP BY and MIN() works fine and is often more portable. Window functions like ROW_NUMBER() are a cleaner approach but require database support and add a step. Master the subquery version first, then optimize if you have time.
Is this still asked at big tech companies?+
Yes. Dell, Oracle, and TCS all ask it. It's a screening question, not a deep diver. They're testing whether you can write correct SQL under time pressure, not whether you know advanced optimization. If it appears in your OA, treat it as a gimme and move on.
What's the most common mistake?+
Deleting the wrong rows. People identify the IDs to keep correctly but then delete those instead of the ones to remove. Always double-check your WHERE clause logic before running DELETE. In a live OA, a syntax error or reversed logic costs real time. StealthCoder eliminates that risk.
Does the solution change between MySQL and PostgreSQL?+
Yes, noticeably. MySQL allows DELETE with a JOIN directly. PostgreSQL and SQL Server require a subquery or CTE. If your OA specifies the database, know the syntax for that platform. If it doesn't, use a portable subquery approach with GROUP BY and MIN() that works everywhere.
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