SQL and Python Generators | Dataford Interview Questions

Tell me about your experience with SQL and Python, including generators and sequences.

For this exercise, use the provided event tables to identify users who have at least one completed transfer and at least one failed transfer. Keep the answer focused on the data result, not on implementation details.

Output

One row per user who has both a completed and failed transfer
Columns: user_id, user_name, completed_transfers, failed_transfers
Sort by failed_transfers descending, then user_id ascending

Schema

users

Column	Type	Description
user_idPK	INT	Unique user identifier
user_name	VARCHAR(100)	User display name
country_code	VARCHAR(2)	Two-letter country code

transfers

Column	Type	Description
transfer_idPK	INT	Unique transfer identifier
user_id	INT	User who initiated the transfer
status	VARCHAR(20)	Transfer outcome, such as completed or failed
amount	NUMERIC(12,2)	Transfer amount
created_at	TIMESTAMP	Transfer creation timestamp

Your question is SQL and Python Generators. Start with the requirements and the two 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.

Problem