Harden retention cohort matrix
Hard SQL arena: date bucketing, joins, and cohort aggregation
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Missing prerequisites: sql-easy-retention-cohorts
Product wants week-one and week-four retention without double counting returning users. You are working inside an analytics warehouse, and the arena only clears when the result is safe, deterministic, and explainable.
Learn to apply date bucketing, joins, and cohort aggregation in an analytics warehouse while explaining the invariant, safety constraints, and hidden edge cases.
- Demonstrates date bucketing, joins, and cohort aggregation
- Handles the visible sample and hidden edge cases
- Keeps output deterministic and explainable
- Stays read-only
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