January Purchasers vs February | Dataford Interview Questions

Monee wants to identify users who purchased through the Monee app during January 2025 but made no purchase during February 2025. Write a PostgreSQL query that returns these January-only purchasers.

Requirements

Treat any purchase from 2025-01-01 through 2025-01-31 as a January purchase.
Exclude users with at least one purchase from 2025-02-01 through 2025-02-28.
Return each qualifying user once, ordered by user_id ascending.

Schema

users

Column	Type	Description
user_idPK	INTEGER	Unique Monee user identifier
full_name	VARCHAR(100)	User display name
signup_date	DATE	Date the user registered

purchases

Column	Type	Description
purchase_idPK	INTEGER	Unique purchase identifier
user_id	INTEGER	User who made the purchase
purchase_date	DATE	Date of the purchase
amount	NUMERIC(10,2)	Purchase amount

Your question is January Purchasers vs February. Start with the requirements and the two tables in the Question tab.

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