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SQLIntermediate#queries

How do you find and delete duplicate rows?

Group by the duplicate columns with HAVING COUNT(*) > 1 to find them, then delete using ROW_NUMBER to keep exactly one copy.

Example
WITH d AS (
  SELECT id, ROW_NUMBER() OVER (PARTITION BY email ORDER BY id) rn
  FROM users
)
DELETE FROM users WHERE id IN (SELECT id FROM d WHERE rn > 1);

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