Customers Purchased in January Only | Dataford Interview Questions

Kotak's analytics team wants to identify customers who purchased through Kotak's digital commerce channel in January 2025 but made no purchase in February 2025. Write a PostgreSQL query using the customers and purchases tables.

Requirements

Return each qualifying customer's ID, name, and number of January purchases.
Include customers with at least one purchase from January 1 through January 31, 2025.
Exclude any customer with a purchase from February 1 through February 28, 2025.
Sort the results by customer_id ascending.

Schema

customers

Column	Type	Description
customer_idPK	INTEGER	Unique customer identifier
customer_name	VARCHAR(100)	Customer's full name
segment	VARCHAR(30)	Customer segment

purchases

Column	Type	Description
purchase_idPK	INTEGER	Unique purchase identifier
customer_id	INTEGER	Customer associated with the purchase
purchase_date	DATE	Date on which the purchase occurred
amount	NUMERIC(12,2)	Purchase amount
channel	VARCHAR(30)	Purchase channel

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