Top Merchants With Ranking | Dataford Interview Questions

Your question is Top Merchants With Ranking. Start with the requirements and the two tables on the right.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

DoorDash Marketplace analytics needs a ranked view of high-performing merchants for January 2025. Write an efficient PostgreSQL query that filters valid transactions, aggregates merchant performance, and ranks qualifying merchants within each cuisine.

Requirements

Include only active merchants and completed transactions from January 1 through January 31, 2025, with a positive transaction amount.
Require at least two qualifying transactions and at least $90 in total revenue.
Use a window function to rank merchants by total revenue within each cuisine, returning the top two per cuisine.
Return merchant_name, cuisine, qualifying_transactions, total_revenue, and cuisine_rank, ordered by cuisine and rank.

Schema

merchants

Column	Type	Description
merchant_idPK	INT	Unique merchant identifier
merchant_name	VARCHAR(100)	DoorDash merchant name
cuisine	VARCHAR(50)	Cuisine category
is_active	BOOLEAN	Whether the merchant is active

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
merchant_id	INT	Merchant associated with the transaction
transaction_date	DATE	Date the transaction occurred
status	VARCHAR(20)	Transaction processing status
amount	NUMERIC(10,2)	Transaction amount in dollars