leetcode 181 Employees Earning More Than Their Managers 不会分析的数据库复杂度
https://leetcode.com/problems/employees-earning-more-than-their-managers/description/
老师上课没分析这些的复杂度,我大概认为子查询要O(n^2)
一开始,直接用了子查询,2400ms....
# Write your MySQL query statement below
select T.name as Employee
from Employee as T
where T.Salary > (select Employee.salary from Employee where Employee.Id = T.ManagerId);
然后
标程有一个2000ms的,但我也认为他复杂度需要O(n^2)
SELECT
a.Name AS 'Employee'
FROM
Employee AS a,
Employee AS b
WHERE
a.ManagerId = b.Id
AND a.Salary > b.Salary
;
最后一个用了join,确实理论上会比较快一丢丢,但是总体来说我感觉还是O(n^2)啊,1800ms快了很多很多
SELECT
a.Name AS 'Employee'
From
Employee as a join Employee as b
on a.ManagerId = b.Id
where
a.Salary > b.Salary
;
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