Running Sales Totals by Region | Dataford Interview Questions

Walmart Marketplace analysts need a regional view of recent sales performance. Using the reporting date of 2025-03-15, write a PostgreSQL query that calculates daily sales and a running 30-day total for each region.

Requirements

Include sales from 2025-02-14 through 2025-03-15, inclusive.
Exclude rows with a missing region.
Aggregate multiple sales records on the same region and date into daily sales.
Use a window function to calculate the cumulative sales total independently for each region, ordered by sale date.

Output details

Return columns in this order: region, sale_date, daily_sales, and running_total.
Order results by region ascending, then sale_date ascending.
Treat NULL sales amounts as 0.00 when calculating daily sales.

Schema

marketplace_sales

Column	Type	Description
sale_idPK	INT	Unique sale identifier
region	VARCHAR(50)	Walmart Marketplace sales region
sale_date	DATE	Date when the sale occurred
sales_amount	NUMERIC(12,2)	Sale amount in dollars

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