SQL Weekly Sales Comparison | Dataford Interview Questions

AT&T Operations Managers need a weekly view of sales performance across AT&T retail stores. Write a PostgreSQL query that aggregates net sales by store and calendar week, then compares each result with the same store's prior week.

Requirements

Join sales to att_stores so the output includes the AT&T store name and region.
Treat NULL sale amounts as zero and aggregate sales by store and Monday-based week.
Include the prior week's sales, the dollar change, and percentage change. Return NULL for comparisons without a prior week or where the prior week's sales equal zero.
Sort by store ID and week start date.

Schema

att_stores

Column	Type	Description
store_idPK	INT	Unique AT&T store identifier
store_name	VARCHAR(100)	AT&T retail store name
region	VARCHAR(50)	Operating region

sales

Column	Type	Description
sale_idPK	INT	Unique sale identifier
store_id	INT	AT&T store associated with the sale
sale_date	DATE	Date the sale was recorded
amount	NUMERIC(10,2)	Net sale amount, including returns

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