175. 组合两个表

select p.FirstName, p.LastName, a.City, a.State
 from Person p left join Address a
 on p.personid=a.personid

176. 第二高的薪水

select (select distinct salary from Employee order by salary desc  limit 1,1) as SecondHighestSalary

177. 第N高的薪水

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
    set N = N-1;
  RETURN (
      # Write your MySQL query statement below.
      select (select distinct salary from Employee order by salary desc  limit N,1) as SecondHighestSalary
  );
END

178. 分数排名

SELECT score, DENSE_RANK() OVER (ORDER BY score DESC) AS `rank`
FROM (
    SELECT score, ROW_NUMBER() OVER (ORDER BY score DESC) AS rn
    FROM Scores
) s
ORDER BY `rank` ASC;

181. 超过经理收入的员工

select a.name as Employee from Employee a join Employee b 
on a.managerId = b.id where a.salary > b.salary

182. 查找重复的电子邮箱

select distinct a.email  Email from  Person a left join Person b on a.email = b.email where a.id != b.id

183. 从不订购的客户

select a.Name Customers from ( select Name, Orders.Id from Customers left join Orders on Customers.Id = Orders.CustomerId ) a where a.Id is null

SELECT Name AS Customers
FROM Customers
WHERE Id NOT IN (SELECT CustomerId FROM Orders);

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