SQL for Customer Feedback Trends | Dataford Interview Questions

Nordstrom's Operations Manager needs a monthly view of customer feedback from active customers to identify changes in satisfaction over time. Write a PostgreSQL query for feedback submitted during 2025-01-01 through 2025-04-30.

Requirements

Return one row per month with feedback count, average rating, and the percentage of rated feedback with a rating of 4 or 5.
Include only feedback from active customers and exclude feedback outside the requested date range.
Calculate the month-over-month change in average rating using a window function. Round average ratings and percentages to two decimal places.
Sort the final results chronologically.

A feedback row with a NULL rating is still a submission, but it must not be included in the average rating or rated-feedback percentage.

Schema

customers

Column	Type	Description
customer_idPK	INTEGER	Unique customer identifier
customer_name	VARCHAR(100)	Customer name
is_active	BOOLEAN	Whether the customer is active

customer_feedback

Column	Type	Description
feedback_idPK	INTEGER	Unique feedback identifier
customer_id	INTEGER	Customer who submitted the feedback
submitted_at	DATE	Feedback submission date
rating	INTEGER	Optional rating from 1 to 5
channel	VARCHAR(30)	Feedback collection channel
comment	TEXT	Optional customer comment

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Problem