SQL sub-queries with JOIN of small scale chopper

//学生表
CREATE TABLE student(
ID INT PRIMARY KEY,
s_name VARCHAR(16) NOT NULL,
class_id INT NOT NULL);

INSERT INTO student VALUES(1, "qf", 3), (2, "lap", 3), (3, "qfa", 8)

//班级表
CREATE TABLE class(
classID INT PRIMARY KEY ,
className VARCHAR ( 16 ) the NOT  NULL  
); 

the INSERT  the INTO class the VALUES ( . 3 , "liaoshihua"), ( . 8 , "Changan Zip") // two lines following functions are similar: the former with JOIN, which sub-query
 


the SELECT S. ID, s.s_name, c.className the FROM Student S the LEFT the JOIN class C the ON s.class_id = c.classID 

the SELECT s.ID, s.s_name, ( the SELECT c.className the FROM class C the WHERE s.class_id = c.classID) className AS  the FROM student s // here to use the AS statement after the results of a query, modify the query results.