SQL for Last Quarter Purchases | Dataford Interview Questions

Cisco Restaurant + Bar wants a quarterly customer purchase report for Business Analytics. Write a PostgreSQL query that summarizes customer activity during the last completed calendar quarter relative to the reporting date 2025-08-15.

Requirements

Calculate the quarter boundaries dynamically from the reporting date using PostgreSQL date functions.
Return every customer, including customers with no purchases during the quarter.
Show purchase count, total spend, and the date of each customer’s most recent purchase in the quarter.
Sort by total spend descending, then customer_id ascending. Exclude purchases outside the quarter, including those on the quarter-end boundary.

Schema

customers

Column	Type	Description
customer_idPK	INTEGER	Unique customer identifier
customer_name	VARCHAR(100)	Customer’s full name
email	VARCHAR(255)	Customer email address

purchases

Column	Type	Description
purchase_idPK	INTEGER	Unique purchase identifier
customer_id	INTEGER	References customers.customer_id
purchased_at	TIMESTAMP	Timestamp when the purchase was made
amount	NUMERIC(10,2)	Purchase amount

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