MySQL查询

内连接 

select   a.*,b.* from tablename a inner join tablename b on a.id=b.id

等于

select a.*,b.* from tablename a,tablename b where a.id=b.id

左连接

select  a.*,b.* from tablename a left join tablename b on a.id=b.id

右连接

select  a.*,b.* from tablename a right join tablename b on a.id=b.id

MySQL查询

原文：https://www.cnblogs.com/siyyawu/p/10805831.html