Join with Date Range — Solution & ExplanationProblems / Join with Date Range / EditorialApproach

JOIN events to subscriptions with a compound condition: same user_id AND event_date BETWEEN start_date AND end_date.

This is a range join — instead of matching on exact equality, we check if the event falls within a date range.

Events outside all subscription periods for their user won't appear.

Key InsightRange joins are common in temporal data (subscriptions, sessions, validity periods). A single event can match multiple subscriptions if they overlap, and some events may not match any subscription at all.Hints

Use BETWEEN in the ON clause to check if event_date falls within the subscription period.

The join has two parts: user_id equality AND date range check.

An event can match multiple subscriptions if a user had overlapping periods.

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