[MySQL] UNION
\n\nSELECT employee_id FROM Employees WHERE employee_id NOT IN (SELECT employee_id FROM Salaries)\nUNION \nSELECT employee_id FROM Salaries WHERE employee_id NO
\n```\nSELECT employee_id FROM Employees WHERE employee_id NOT IN (SELECT employee_id FROM Salaries)\nUNION \nSELECT employee_id FROM Salaries WHERE employee_id NOT IN (SELECT employee_id FROM Employees)\nORDER BY 1\n```
['MySQL']