Running Total SQL | Dataford Interview Questions

The Tata Consultancy Services North America sales team tracks TCS BaNCS implementation revenue across client accounts. Write a PostgreSQL query that reports monthly North American sales and the cumulative sales total through each month.

Requirements

Join sales transactions to client accounts and include only accounts in the North America region.
Restrict transactions to January through April 2025 and aggregate sales by calendar month.
Calculate a running total of monthly sales in chronological order using a window function.
Return the month as YYYY-MM, monthly sales, and the running total, ordered from earliest to latest month.

Schema

tcs_client_accounts

Column	Type	Description
account_idPK	INTEGER	Unique client account identifier
account_name	VARCHAR(100)	Client account name
region	VARCHAR(50)	Client sales region

tcs_sales_transactions

Column	Type	Description
transaction_idPK	INTEGER	Unique sales transaction identifier
account_id	INTEGER	References tcs_client_accounts.account_id
sale_date	DATE	Date of the sale
amount	NUMERIC(12,2)	Sales amount in USD

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