Find Duplicate Records in SQL | Dataford Interview Questions

Johns Hopkins Medicine needs to identify duplicate patient records before a data quality cleanup. Write a SQL query to find records that appear more than once based on the same first_name, last_name, and date_of_birth.

Requirements

Return each duplicated name and birth date combination only once
Include the number of times each duplicate appears
Sort results by duplicate count descending, then by name

Schema

patient_records

Column	Type	Description
patient_idPK	INT	Primary key for each patient record
first_name	VARCHAR(100)	Patient first name
last_name	VARCHAR(100)	Patient last name
date_of_birth	DATE	Patient date of birth
mrn	VARCHAR(20)	Medical record number
created_at	TIMESTAMP	Record creation timestamp

Your question is Find Duplicate Records in SQL. Start with the requirements and the one table in the Question tab.

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Problem

Requirements

Return each duplicated name and birth date combination only once
Include the number of times each duplicate appears
Sort results by duplicate count descending, then by name

Schema

patient_records

Column	Type	Description
patient_idPK	INT	Primary key for each patient record
first_name	VARCHAR(100)	Patient first name
last_name	VARCHAR(100)	Patient last name
date_of_birth	DATE	Patient date of birth
mrn	VARCHAR(20)	Medical record number
created_at	TIMESTAMP	Record creation timestamp

Your question is Find Duplicate Records in SQL. 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.