Self-Join SQL Query | Dataford Interview Questions

Write a self-join SQL query.

Using the employees table, return each unique unordered pair of employees who share the same non-null manager. Do not return an employee paired with themselves or repeat the same pair in reverse order.

Output

One row per employee pair
Columns: manager_id, employee_1_id, employee_1_name, employee_2_id, employee_2_name
Order by manager_id, employee_1_id, then employee_2_id ascending

Schema

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee name
manager_id	INT	Identifier of the employee's manager
department	VARCHAR(80)	Employee department

Your question is Self-Join SQL Query. 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 self-join SQL query.

Output

One row per employee pair
Columns: manager_id, employee_1_id, employee_1_name, employee_2_id, employee_2_name
Order by manager_id, employee_1_id, then employee_2_id ascending

Schema

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee name
manager_id	INT	Identifier of the employee's manager
department	VARCHAR(80)	Employee department

Your question is Self-Join SQL Query. 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.