leetcode 刷题

select (select distinct salary from employee order by salary limit 1 offset 1) as secondhighestsalary;  ---去掉第一个，再从第一个开始

------相关子查询：子查询中引用了外层查询所引用表的字段

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN

  RETURN (
      # Write your MySQL query statement below.
    select max(salary) from employee e1
      where N=(select count(distinct salary) from employee e2
              where e2.salary >=e1.salary)
  );
END
----执行步骤，1.从父查询中取出每一条salary，与子查询中的e2.salary进行比较，直到当大于e2.salary的记录等于n
            2.父查询输出最大的salary

---相关子查询
---方法一
select score,(select count(distinct score) from scores e1 where e1.score>= e2.score) rank
from scores e2 
order by rank;