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Quick Summary
Compute weekly user churn rates for a specified month based on activity logs.
Align dates to Monday-starting periods and remove duplicate user entries per week.
Compare consecutive weeks to calculate retention ratios while excluding terminal periods without a successor.
What This Tests
Date arithmetic and period alignment
Self-referential joining for cohort tracking
Aggregation with conditional counting
Group-level filtering for boundary conditions
Pre-aggregation deduplication
Common Patterns
Self Join
Aggregation
Date Arithmetic
HAVING Filter
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