Leetcode:608 tree node

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One 、code

1.1 Title Description

Address

1.2 Answer key

# 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' #  When not in（）  It contains null value , The query will not return any value .
        else 'Leaf'
    end as type
from 
    tree
order by id
;

Two 、 summary

select case city_name
when ‘ Shenzhen ’ THEN ‘ south China ’
when ‘ Guangzhou ’ THEN ‘ south China ’
when ‘ foshan ’ THEN ‘ south China ’
when ‘ Hangzhou ’ THEN ‘ East China ’
when ‘ Shanghai ’ THEN ‘ East China ’
ELSE ‘ other ’
END AS temp,