PostgreSQL Active Customer Usage Report | Dataford Interview Questions

What are the most important SQL joins you use for complex reporting?

Write a PostgreSQL query that demonstrates this reporting task using the provided tables. Include active customers, their active subscription details when available, and usage events during the first quarter of 2026.

Output

One row per active customer, with customer_id, customer_name, plan_name, event_count, and engagement_status.
Use No active subscription when no active subscription exists and Unspecified when an active subscription has no plan name.
Sort by event_count descending, then customer_id ascending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer display name
customer_status	VARCHAR(30)	Current customer status

subscriptions

Column	Type	Description
subscription_idPK	INT	Unique subscription identifier
customer_id	INT	Customer owning the subscription
plan_name	VARCHAR(100)	Subscription plan name
subscription_status	VARCHAR(40)	Current subscription status

usage_events

Column	Type	Description
event_idPK	INT	Unique usage event identifier
customer_id	INT	Customer associated with the event
event_date	DATE	Date the usage event occurred
event_type	VARCHAR(50)	Type of product usage event

Your question is PostgreSQL Active Customer Usage Report. Start with the requirements and the three tables in the Question tab.

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