[코드카타] SQL 21 Replace Employee ID With The Unique Identifier

[코드카타] SQL 21 Replace Employee ID With The Unique Identifier

21. Replace Employee ID With The Unique Identifier
https://leetcode.com/problems/replace-employee-id-with-the-unique-identifier/

Write a solution to show the unique ID of each user, 
If a user does not have a unique ID replace just show null.
Return the result table in any order.

select unique_id, name
from Employees a
left join EmployeeUNI b on a.id = b.id

#join여부