Running Subscriber Total by Region | Dataford Interview Questions

Write a window function to calculate the running total of active subscribers over time, grouped by region, for Nyc Staffing.

Use valid activation and deactivation events for subscribers with a known region. The running count should reflect each region's cumulative net change through each event date.

Output

One row per region and event date with at least one valid status event
Columns: region, event_date, and active_subscriber_count
Include only non-null regions and valid activation or deactivation events
Order by region, then event_date ascending

Schema

subscribers

Column	Type	Description
subscriber_idPK	INT	Unique subscriber identifier
subscriber_name	VARCHAR(100)	Subscriber display name
region	VARCHAR(50)	Subscriber region

subscriber_status_events

Column	Type	Description
event_idPK	INT	Unique status event identifier
subscriber_id	INT	Subscriber associated with the event
event_date	DATE	Date of the status change
event_type	VARCHAR(20)	Subscriber status change type

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Problem