Delete Duplicates in SQL | Dataford Interview Questions

SQL: delete duplicate rows.

Asked in the R1 stage as one of 2-3 easy SQL questions. Write a PostgreSQL query that removes duplicate rows from sales_records, keeping the row with the smallest id for each identical set of non-id values.

Output

One row per deleted duplicate
Column: deleted_id
Include only rows removed by the query; ordering is not required

Schema

sales_records

Column	Type	Description
idPK	INT	Unique sales record identifier
store_id	INT	Store identifier
product_sku	VARCHAR(30)	Product stock keeping unit
sale_date	DATE	Date of sale
quantity	INT	Units sold
unit_price	DECIMAL(10,2)	Price per unit

Your question is Delete Duplicates 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.

Problem

SQL: delete duplicate rows.

Output

One row per deleted duplicate
Column: deleted_id
Include only rows removed by the query; ordering is not required

Schema

sales_records

Column	Type	Description
idPK	INT	Unique sales record identifier
store_id	INT	Store identifier
product_sku	VARCHAR(30)	Product stock keeping unit
sale_date	DATE	Date of sale
quantity	INT	Units sold
unit_price	DECIMAL(10,2)	Price per unit

Your question is Delete Duplicates 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.