FAANG SQL Interview Pattern #8 — Finding Duplicates * Deduplication in SQL
Every dataset is messy. Every data engineer eventually writes this query. And it shows up constantly at Amazon, Google, and Microsoft.
In this episode we build the duplicates pattern from scratch — detection with GROUP BY and HAVING, surgical de-duplication with ROW_NUMBER OVER (PARTITION BY ... ORDER BY ...), the DELETE finisher — then apply it end-to-end on two real FAANG interview questions.
📌 The pattern in one breath: decide your business keys, GROUP BY to detect, ROW_NUMBER to pick the winner, WHERE rn = 1 to keep, WHERE rn greater than 1 to delete. Always SELECT before you DELETE.
⏱️ Chapters
00:00 — The Amazon orders problem
01:49 — What actually counts as a duplicate?
05:24 — Building the three queries (GROUP BY, ROW_NUMBER, DELETE)
10:33 — The 5 pitfalls that wreck candidates
14:11 — 🟧 FAANG Q1 — Amazon: de-duplicate order retries
19:16 — 🟦 FAANG Q2 — Google: detect and DELETE duplicate emails
24:12 — Recap and key takeaway
25:35 — Next episode: Sessionization
📺 SQL Interview Patterns — FAANG Edition · Episode 08
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