Left Join

左连接查询，以左边为主表。

1

select a.*,b.name from a left join b on a.id = b.a_id;

Right Join

右连接查询，以右边为主表。

1

select b.*,a.name from a right join b on a.id = b.a_id;

Inner Join

内连接查询，以左右表交集。

1

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

In

范围查询

1

select a.* from a where a.id in ('1','3')

Exist

是否存在数据查询

1

select * from a where exist (select 1 from b on a.id=b.a_id and b.grade>100)