Fast MySQL solution using UNION and GROUP BY with brief explanation
Steps:\n1. select all the employee_ids from 2 tables\n2. find out the employee_id which appears only once\n\nfor example:\ntable 1=[1,2,5], table 2=[1,4,5]\nSte
Steps:\n1. select all the employee_ids from 2 tables\n2. find out the employee_id which appears only once\n\nfor example:\ntable 1=[1,2,5], table 2=[1,4,5]\nStep 1. select all the employee_ids with UNION ALL\n-> 1, 1, 2, 4, 5, 5\nStep 2. find those employee_ids which appear only once\n-> 2, 4\n```\n# Write your MySQL query statement below\nSELECT employee_id FROM\n(\n\t# select all the employee_ids from 2 tables (eg. [1, 1, 2, 4, 5, 5])\n    SELECT employee_id FROM Employees\n    UNION ALL SELECT employee_id FROM Salaries\n) t\nGROUP BY employee_id\nHAVING COUNT(*)=1\nORDER BY employee_id;\n```
[]