sql中left joinright join与inner join的区别

Posted 2021-01-12 RobotsRising

1、数据库

1.1、作者表

 

1.2、图书表

1.3、出版社表

2、left join

　　left join(左联接) 返回包括左表中的所有记录和右表中联结字段相等的记录。

2.1、sql语句

select * from app01_publisher left join app01_book on app01_publisher.id = app01_book.publish_id

 

2.2、查询结果

3、right join

　　right join(右联接) 返回包括右表中的所有记录和左表中联结字段相等的记录。

3.1、sql语句

select * from app01_publisher right join app01_book on app01_publisher.id = app01_book.publish_id

 

3.2、查询结果

4、innner join

　　inner join(等值连接) 只返回两个表中联结字段相等的行。

4.1、sql语句

select * from app01_publisher inner join app01_book on app01_publisher.id = app01_book.publish_id

 

4.2、查询结果