LeetCode - 584. Find Customer Referee (MySQL)

Easy, SQL - NULL 처리

RunTime : 963 ms

문제

Find the names of the customer that are not referred by the customer with id = 2.

Return the result table in any order.

The result format is in the following example.

풀이

• 처음엔 단순히 referee_id != 2 이거만 했는데, NULL처리가 안되어 틀렸다.
• NULL이 포함되어 있을 땐, NULL처리도 확실히 해줘야 한다.

SELECT name FROM Customer
WHERE referee_id IS NULL OR referee_id != 2