Leetcode:608 树节点

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一、code

1.1 题目描述

地址

1.2 题解

# Write your MySQL query statement below
select 
    id,
    case
        when p_id is null then 'Root'
        when id in (select distinct p_id from tree) then 'Inner' # 当not in（） 里面包含null值，查询不会返回任何值。
        else 'Leaf'
    end as type
from 
    tree
order by id
;

二、总结

select case city_name
when ‘深圳’ THEN ‘华南’
when ‘广州’ THEN ‘华南’
when ‘佛山’ THEN ‘华南’
when ‘杭州’ THEN ‘华东’
when ‘上海’ THEN ‘华东’
ELSE ‘其他’
END AS temp,