mysql基础

mysql基础知识

1.创建数据库

mysql> CREATE DATABASE IF NOT EXISTS homestead DEFAULT CHARSET utf8mb4 COLLATE utf8mb4_unicode_ci;
mysql> CREATE DATABASE IF NOT EXISTS abc DEFAULT CHARSET utf8 COLLATE utf8_general_ci;

2.连接查询

1.内连接（INNER JOIN）

等值连接
        SELECT A.*, B.*  
        FROM student_info A inner join student_score B  
        ON A.student_id = B.student_id   
非等值连接
        SELECT A.*, B.*  
        FROM student_info A inner join student_score B  
        ON A.student_id > B.student_id

2.左外连接（LEFT OUTER JOIN）

SELECT A.*, B.*  
FROM student_info A left join student_score B  
ON A.student_id = B.student_id 

3.右外连接（RIGHT OUTER JOIN）

SELECT A.*, B.*  
FROM student_info A right join student_score B  
ON A.student_id = B.student_id