MySQL left Join,right Join,inner join Simple instance

--preparatory work

drop table if exists Emp;
CREATE table if not exists EMP
(
UID INT primary KEY,
Sid int
);
INSERT into EMP values (+);
INSERT into EMP values (2,2);

drop table if exists Sal;
CREATE table if not exists Sal
(
Sid Int Primary KEY,
Salary float
);
INSERT into Sal values (1,11);
INSERT into Sal values (3,33);

--View Results
SELECT * from EMP LEFT join Sal on emp.sid = Sal.sid;

The left table is the main (the left table content appears at least once)

Uid	Sid	Sid	Salary
1	1	1	11
2	2	Null	Null

SELECT * from EMP right join Sal on emp.sid = Sal.sid;

The right table is the main (the right table content appears at least once)

Uid	Sid	Sid	Salary
1	1	1	11
Null	Null	3	33

SELECT * FROM EMP inner join Sal on emp.sid = Sal.sid;

The equivalent of the above two tables to find the intersection

Uid	Sid	Sid	Salary
1	1	1	11

MySQL left Join,right Join,inner join Simple instance