Joins Across Customer, Transaction, Merchant | Dataford Interview Questions

Write a SQL query using joins to combine customer, transaction, and merchant tables.

Return one row for every transaction, including transactions whose customer or merchant reference is missing.

Output

Columns: transaction_id, transaction_date, customer_name, transaction_amount, merchant_name, and merchant_category
Use Unknown customer, Unknown merchant, or Uncategorized when the related value is missing
Order by transaction_date ascending, then transaction_id ascending

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer full name
customer_segment	VARCHAR(30)	Customer segmentation label

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
customer_id	INT	Customer associated with the transaction
merchant_id	INT	Merchant associated with the transaction
transaction_date	DATE	Date the transaction occurred
transaction_amount	NUMERIC(12,2)	Transaction amount

merchants

Your question is Joins Across Customer, Transaction, Merchant. Start with the requirements and the three tables in the Question tab.

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