Here is solution with left join and union
sql\nSELECT e.employee_id \nFROM Employees e\nLEFT JOIN Salaries s ON e.employee_id = s.employee_id\nWHERE s.employee_id IS NULL\nUNION \nSELECT s.employee_id \
```sql\nSELECT e.employee_id \nFROM Employees e\nLEFT JOIN Salaries s ON e.employee_id = s.employee_id\nWHERE s.employee_id IS NULL\nUNION \nSELECT s.employee_id \nFROM Salaries s\nLEFT JOIN Employees e ON e.employee_id = s.employee_id\nWHERE e.employee_id IS NULL\nORDER BY employee_id\n```
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