关于MySQL多表连接查询

select a.*,c.device_name from device_warn as a 
inner join user_warn as b
on a.id=b.warn_id and b.state=1 inner join 
device_info as c 
on c.DEVICE_ID=a.DEVICE_ID 
where a.DEVICE_ID in (select DEVICE_ID from device_station where STATION_ID in (select STATION_ID from station_user where USER_ID=4))

本条sql语句涉及到了三个表的联查，分别是device_warn，user_warn，device_info，

其中，device_warn，user_warn，device_info的表结构分别如下：

易错问题，where条件必须在join条件之后。