Running Totals SQL Query | Dataford Interview Questions

Your question is Running Totals SQL Query. Start with the requirements and the two tables on the right.

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Problem

Resideo's Smart Home platform tracks customer purchases associated with its connected-home products. Write a PostgreSQL query that reports each customer's completed purchase total by date and the cumulative total through that date.

Requirements

Include only purchases with status = 'completed' and a non-null purchase_date.
Aggregate multiple purchases for the same customer on the same date into one daily total.
Treat a null amount as zero.
Calculate a running total that resets for each customer and order the final results by customer and date.

Schema

customers

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

smart_home_purchases

Column	Type	Description
purchase_idPK	INT	Unique purchase identifier
customer_id	INT	Customer associated with the purchase
purchase_date	DATE	Date when the purchase was recorded
amount	NUMERIC(10,2)	Purchase amount
status	VARCHAR(20)	Purchase processing status