SQL Duplicate Detection | Dataford Interview Questions

Euronet Worldwide needs to identify duplicate customer profiles in its customer master table before downstream payment and transfer workflows use the wrong record. Write a SQL query to find all duplicated profiles based on the same first name, last name, and date of birth.

Requirements

Return each duplicate profile group once, with the shared identifying fields.
Include a duplicate_count showing how many rows share that profile.
Only return groups with more than one row.
Sort results by duplicate_count descending, then by name.

Schema

customer_profiles

Column	Type	Description
customer_idPK	INT	Primary key for the profile record
first_name	VARCHAR(100)	Customer first name
last_name	VARCHAR(100)	Customer last name
date_of_birth	DATE	Customer date of birth
email	VARCHAR(255)	Contact email, may be NULL
created_at	TIMESTAMP	Record creation timestamp

Your question is SQL Duplicate Detection. 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

Requirements

Return each duplicate profile group once, with the shared identifying fields.
Include a duplicate_count showing how many rows share that profile.
Only return groups with more than one row.
Sort results by duplicate_count descending, then by name.

Schema

customer_profiles

Column	Type	Description
customer_idPK	INT	Primary key for the profile record
first_name	VARCHAR(100)	Customer first name
last_name	VARCHAR(100)	Customer last name
date_of_birth	DATE	Customer date of birth
email	VARCHAR(255)	Contact email, may be NULL
created_at	TIMESTAMP	Record creation timestamp

Your question is SQL Duplicate Detection. 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.