三个select联合查询,查询结果先以第一个表的字段排序，再以第二个表的字段排序，最后以第三个表的字段排序，怎么写啊
------解决方案--------------------
select * from
(
select a.SubmitInfoRID ,1 as woyaomm
from t_event_submitInfo t
left join t_event_submitOppose a on t.rid=a.SubmitInfoRID
left join t_base_dept b on a.subopposerRID=b.rid
union ALL
select a.SubmitInfoRID ,2 as woyaomm
from t_event_submitInfo t
left join t_event_submitOppose a on t.rid=a.SubmitInfoRID
left join t_base_outdept c on a.subopposerRID=c.rid
union ALL
select a.SubmitInfoRID ,3 as woyaomm
from t_event_submitInfo t
left join t_event_submitOppose a on t.rid=a.SubmitInfoRID
left join t_base_watchfix d on a.subopposerRID=d.rid
) as SubmitOpposer
order by woyaomm ,SubmitInfoRID