Strictly Increasing Prices Query | Dataford Interview Questions

Nielsen pricing analysts want to identify products with consistently rising observed prices in the Nielsen product catalog. Write a PostgreSQL query that returns product names whose non-null monthly prices strictly increase over time.

Requirements

Join the product catalog to its monthly pricing records.
Use a window function to compare each price with the previous observed month for the same product.
Return products with at least three non-null monthly prices, where every subsequent price is strictly greater than the previous one.
Sort the resulting product names alphabetically. Missing calendar months do not invalidate a product; compare the available non-null observations in chronological order.

Schema

nielsen_products

Column	Type	Description
product_idPK	INT	Unique Nielsen product identifier
product_name	VARCHAR(150)	Nielsen product name
category	VARCHAR(80)	Product category

nielsen_monthly_prices

Column	Type	Description
price_idPK	INT	Unique pricing record identifier
product_id	INT	Referenced Nielsen product identifier
month_start	DATE	First day of the pricing month
price	NUMERIC(10,2)	Observed product price

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