Overlapping Subscription Periods per Customer

Return every pair of subscriptions for the same customer whose inclusive active periods overlap. A NULL end_date means the subscription is still active. Return customer_id, subscription_a, subscription_b, overlap_start and overlap_end; use NULL overlap_end for an open-ended overlap. Return columns: customer_id, subscription_a, subscription_b, overlap_start, overlap_end.

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Challenge overview

What you will practice

Return every pair of subscriptions for the same customer whose inclusive active periods overlap. A NULL end_date means the subscription is still active. Return customer_id, subscription_a, subscription_b, overlap_start and overlap_end; use NULL overlap_end for an open-ended overlap. Return columns: customer_id, subscription_a, subscription_b, overlap_start, overlap_end.

Difficulty: Advanced
SQL concept: INNER JOIN