SELECT *
FROM a
full outer join b
ON a.xx=b.xx --#1.a和b先产生一个结果集
inner join C
on a.xx=c.xx and b.xx=c.xx --#2.上面的结果集看成一个表,再和C表INNSER JOIN
------解决方案-------------------- it depends, ms database engine could do some tunnings, it may not follow the t-sql table order. You can check sql server excution plan. ------解决方案-------------------- 连接是很费资源的 ------解决方案--------------------