[LeetCode]584. Find Customer Referee

SQL I 筆記撰寫計畫

敘述

這是 SQL I 的第一天第三個題目，總共有四題。

• 難度: Easy
• 花費時間: 1min
• 題目

給你一張表 Customer ，找出裡面 referee_id 不是 2 的。

Table: Customer

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| name        | varchar |
| referee_id  | int     |
+-------------+---------+
id is the primary key column for this table.
Each row of this table indicates the id of a customer, their name, and the id of the customer who referred them.

Example 1:

Input: 
Customer table:
+----+------+------------+
| id | name | referee_id |
+----+------+------------+
| 1  | Will | null       |
| 2  | Jane | null       |
| 3  | Alex | 2          |
| 4  | Bill | null       |
| 5  | Zack | 1          |
| 6  | Mark | 2          |
+----+------+------------+
Output: 
+------+
| name |
+------+
| Will |
| Jane |
| Bill |
| Zack |
+------+

筆記

簡單的 select function 如下:

select name from Customer
where referee_id <> 2 # 大於小於 2 的
or referee_id is null # null 並不大於小於 2 因此單獨處理

成績