✅ MySQL Solution, 2 Approaches
Approach 1:\n\nSELECT employee_id FROM Employees \nWHERE employee_id NOT IN (SELECT employee_id FROM Salaries)\nUNION\nSELECT employee_id FROM Salaries \nWHERE 
**Approach 1:**\n```\nSELECT employee_id FROM Employees \nWHERE employee_id NOT IN (SELECT employee_id FROM Salaries)\nUNION\nSELECT employee_id FROM Salaries \nWHERE employee_id NOT IN (SELECT employee_id FROM Employees)\nORDER BY employee_id;\n```\n\n\n**Approach 2:**\n```\nSELECT Sub.employee_id FROM\n(SELECT e.employee_id, name, salary\nFROM Employees AS e \nLEFT JOIN \nSalaries AS s\nON e.employee_id = s.employee_id\nUNION\nSELECT s.employee_id, name, salary\nFROM Employees AS e \nRIGHT JOIN \nSalaries AS s\nON e.employee_id = s.employee_id) AS Sub\nWHERE Sub.name IS NULL OR Sub.salary IS NULL\nORDER BY Sub.Employee_id;\n```
['Union Find', 'MySQL']