MySQL问题求助呀各位大神！！！

如下有三张表：Students表，Friends表和Salary表，请问：如何找出朋友工资比自己高的人？

以下是创建三张表的代码。

create table Students(
ID1 int NOT NULL ,
s_name char(10) NOT NULL ,
primary key(ID1)
)ENGINE=InnoDB;
create table Friends(
ID2 int NOT NULL ,
Friend_ID int NOT NULL ,
primary key(ID2)
)ENGINE=InnoDB;
create table Salaries(
ID3 int NOT NULL ,
Salaries char(10) NOT NULL ,
primary key(ID3)
)ENGINE=InnoDB;

insert into Students(ID1,
s_name)
values('1','甲'),
('2','乙'),
('3','丙'),
('4','丁');
insert into Friends(ID2,
Friend_ID)
values('1','2'),
('2','3'),
('3','4'),
('4','1');
insert into Salaries(ID3,
Salaries)
values('1','2000'),
('2','1000'),
('3','5000'),
('4','10000');

SELECT s.ID,sa.Salaries,f.ID,sa2.Salaries
FROM students s
LEFT JOIN Friends f ON s.id = f.Friend_ID
LEFT JOIN Salaries sa on sa.id = s.id
LEFT JOIN Salaries sa2 on f.id = sa2.id
WHERE sa2.Salaries < sa.Salaries
看一下是不是要的结果