A simple Solution in PostgreSQL
\nSELECT e.employee_id FROM Employees e \n\tLEFT JOIN salaries s ON e.employee_id = s.employee_id\n\t\tWHERE s.salary IS NULL\nUNION\nSELECT s.employee_id FROM 
```\nSELECT e.employee_id FROM Employees e \n\tLEFT JOIN salaries s ON e.employee_id = s.employee_id\n\t\tWHERE s.salary IS NULL\nUNION\nSELECT s.employee_id FROM Salaries s \n\tLEFT JOIN employees e ON e.employee_id = s.employee_id\n\t\tWHERE e.name IS NULL;\n```
['Union Find']