MySQL | 3 Different approaches
\n# Solution 1\n\nSELECT employee_id \nFROM Salaries \nWHERE employee_id NOT IN (SELECT employee_id \n                             FROM Employees\n             
\n# Solution 1\n```\nSELECT employee_id \nFROM Salaries \nWHERE employee_id NOT IN (SELECT employee_id \n                             FROM Employees\n                           )\nUNION\n\nSELECT employee_id \nFROM Employees \nWHERE employee_id NOT IN (SELECT employee_id \n                             FROM Salaries\n                           )\nORDER BY employee_id\n```\n\n# Solution 2\n```\nSELECT T.employee_id from\n(\n    SELECT * FROM Employees \n    UNION ALL\n    SELECT * FROM Salaries\n) T\n\nGROUP BY T.EMPLOYEE_ID\nHAVING COUNT(T.EMPLOYEE_ID) = 1   /*can also use count(*) */\nORDER BY T.EMPLOYEE_ID ASC\n```\n\n# Solution 3\nNote - Doesn\'t work here in LEETCODE but this is also a potenstial solutin to solve this problem during interviews.\n\n```\nSELECT ISNULL(A.employee_id,B.employee_id) AS employee_id\nFROM Employees A\nFULL OUTER JOIN Salaries B\nON A.employee_id = B.employee_id\nWHERE A.name IS NULL OR B.salary IS NULL\nORDER BY employee_id\n```
['Union Find', 'MySQL']