Self-Join Use Case | Dataford Interview Questions

Can you describe a self-join in SQL and provide a scenario where it would be useful?

Using an employees table, demonstrate the concept by returning employees who have a matching direct manager. Provide a PostgreSQL query and briefly explain why this pattern is useful.

Output

One row per employee with a matching manager
Columns: employee_name, manager_name, and department
Sort by manager_name, then employee_name alphabetically

Schema

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee's full name
manager_id	INT	Employee identifier of the direct manager
department	VARCHAR(100)	Employee department

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