✅✅ MYSQL || Union || Two approaches || Left Join || Sub-query
Please Upvote if you found this helpful.\nSUBQUERY:\n\nselect employee_id from Employees where employee_id not in  (select  employee_id from Salaries)\nunion \n
### *Please Upvote if you found this helpful.*\n**SUBQUERY:**\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 employee_id;\n```\n\n**JOINS:**\n```\nselect e.employee_id from Employees e  \nleft join Salaries s on e.employee_id=s.employee_id\nwhere salary is null \nunion \nselect s.employee_id from Salaries s\nleft join Employees e  on e.employee_id=s.employee_id\nwhere name is null \norder by employee_id;\n```
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