mysql的七种join连接查询

mysql join查询是开发中必不可少的知识，以下整理了常见的七种join查询语句，方便学习

一、内连接

sleect * from a inner join b on a.key = b.ky;

二、左连接

select * from a left join b on a.key = b.key;

三、右连接

select * from a right join b on a.key - b.key;

四、左独占

select * from a left join b on a.key = b.key where b.kry is null;

五、右独占

select * from a right join b on a.key = b.key where a.key is null;

六、全连接

select * from a left join b on a.key = b.key union select * from a right join b on a.key = b.key;

七、全独占

seelct * from a left join a on a.key = b.key where a.key is null union select * from a right join b on a.key = b.key where b.key is null;