Fast NOT EXISTS + UNION Solution
\nSELECT employee_id FROM Employees e\nWHERE NOT EXISTS (SELECT employee_id FROM Salaries s WHERE e.employee_id = s.employee_id)\n\nUNION \n\nSELECT employee_id
```\nSELECT employee_id FROM Employees e\nWHERE NOT EXISTS (SELECT employee_id FROM Salaries s WHERE e.employee_id = s.employee_id)\n\nUNION \n\nSELECT employee_id FROM Salaries s\nWHERE NOT EXISTS (SELECT employee_id FROM Employees e WHERE e.employee_id = s.employee_id)\n\nORDER BY employee_id\n```
['Union Find']