Window Functions Running Total | Dataford Interview Questions

Samba TV's measurement team wants to monitor cumulative sales associated with active advertising campaigns. Write a PostgreSQL query that aggregates sales by campaign and date, then calculates a chronological running total for each active campaign.

Requirements

Include only campaigns whose status is active.
Aggregate sales_amount by campaign and sale_date, treating missing or null sales amounts as zero.
Calculate a separate running total for each campaign, ordered by sale date.
Include active campaigns with no sales, and sort the final output by campaign name and sale date.

Schema

campaigns

Column	Type	Description
campaign_idPK	INT	Unique campaign identifier
campaign_name	VARCHAR(100)	Samba TV campaign name
status	VARCHAR(20)	Campaign lifecycle status
advertiser	VARCHAR(100)	Advertiser associated with the campaign

campaign_sales

Column	Type	Description
sale_idPK	INT	Unique sales record identifier
campaign_id	INT	Referenced campaign identifier
sale_date	DATE	Date on which the sale was attributed
sales_amount	NUMERIC(12,2)	Attributed sales amount
source	VARCHAR(30)	Attribution source

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