Find Duplicate Registrations | Dataford Interview Questions

Write a SQL query to find the duplicate records in a test-taker registration table. Treat rows with the same test_taker_id, test_code, and registration_date as duplicates. Return one row per duplicated combination, including the source registration IDs.

Output

Columns: test_taker_id, test_code, registration_date, duplicate_count, and registration_ids
Include only combinations appearing more than once
Sort by test_taker_id, test_code, and registration_date ascending

Schema

test_taker_registrations

Column	Type	Description
registration_idPK	INT	Unique registration record identifier
test_taker_id	INT	Identifier for the test taker
test_code	VARCHAR(20)	ETS assessment code
registration_date	DATE	Date associated with the registration

Your question is Find Duplicate Registrations. Start with the requirements and the one table 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

Output

Columns: test_taker_id, test_code, registration_date, duplicate_count, and registration_ids
Include only combinations appearing more than once
Sort by test_taker_id, test_code, and registration_date ascending

Schema

test_taker_registrations

Column	Type	Description
registration_idPK	INT	Unique registration record identifier
test_taker_id	INT	Identifier for the test taker
test_code	VARCHAR(20)	ETS assessment code
registration_date	DATE	Date associated with the registration

Your question is Find Duplicate Registrations. Start with the requirements and the one table 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.