Find and Remove Duplicate Records | Dataford Interview Questions

Write a query to find duplicate records in a table based on a specific column, and explain how you would delete them.

Use customer_accounts and treat email as the column that must be unique. Keep the record with the smallest id, exclude NULL emails from duplicate detection, and explain how to delete only the later duplicate records.

Output

One row per record marked for deletion, with duplicate_id, email, created_at, and duplicate_count.
Exclude the retained record and rows whose email is NULL.
Order by email ascending, then duplicate_id ascending.

Schema

customer_accounts

Column	Type	Description
idPK	INTEGER	Unique account record identifier
email	VARCHAR(255)	Email value used to identify duplicates
created_at	TIMESTAMP	Time when the account record was created

Your question is Find and Remove Duplicate Records. 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

Write a query to find duplicate records in a table based on a specific column, and explain how you would delete them.

Output

One row per record marked for deletion, with duplicate_id, email, created_at, and duplicate_count.
Exclude the retained record and rows whose email is NULL.
Order by email ascending, then duplicate_id ascending.

Schema

customer_accounts

Column	Type	Description
idPK	INTEGER	Unique account record identifier
email	VARCHAR(255)	Email value used to identify duplicates
created_at	TIMESTAMP	Time when the account record was created

Your question is Find and Remove Duplicate Records. 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.