Running Total Over Telecom Usage | Dataford Interview Questions

Rakuten Symphony's network operations teams need a chronological view of completed telecom usage by service region. Write a PostgreSQL query that aggregates usage by region and day, then calculates a running total for each region.

Requirements

Join usage events to Rakuten Symphony network sites to obtain the region.
Include only completed events from February 2025.
Treat NULL usage values as zero when calculating daily and cumulative usage.
Return region, usage date, daily usage in MB, and the regional running total, ordered by region and date.

Schema

network_sites

Column	Type	Description
site_idPK	INTEGER	Unique network site identifier
site_name	VARCHAR(100)	Human-readable site name
region	VARCHAR(50)	Service region containing the site

usage_events

Column	Type	Description
event_idPK	INTEGER	Unique usage event identifier
site_id	INTEGER	Network site associated with the event
usage_date	DATE	Date of recorded usage
usage_mb	NUMERIC(12,2)	Usage volume in megabytes
event_status	VARCHAR(20)	Usage event processing status

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