请教一个SQL查询问题

Question

table_1:
zhuti_id(int)   zhuti_addtime(datetime)   zhuti_state(int)
-------------------------------------------------
   1           2007-4-1 10:00:00         0
   2           2007-4-2 10:00:00         1
   3           2007-4-3 10:00:00         0
   4           2007-4-4 10:00:00         2
table_2:
huifu_zhutiid(int)   huifu_addtime(datetime)
--------------------------------------------------
   1                 2007-4-1 11:00:00
   1                 2007-4-4 11:00:00
   3                 2007-4-4 10:00:00条件：查询表table_1级联table_2条件zhuti_id = huifu_zhutiid，只级联huifu_addtime最大的那一条，如果huifu_addtime为空，那么huifu_addtime = zhuti_addtime。
排序方法：先按照zhuti_state降序排列，在按照huifu_addtime降序排列。结果：
zhuti_id(int) zhuti_addtime(datetime) zhuti_state(int) huifu_addtime(datetime) huifu_numb(int)
-------------------------------------------------------------------------
     4      2007-4-4 10:00:00          2      2007-4-4 10:00:00    0
     2      2007-4-2 10:00:00          1      2007-4-2 10:00:00    0
     1      2007-4-1 10:00:00          0      2007-4-4 11:00:00    2
     3      2007-4-3 10:00:00          0      2007-4-4 10:00:00    1huifu_numb为huifu_zhutiid在table_2中出现的次数

Answer 1

select zhuti_id,zhuti_addtime,zhuti_state,max(huifu_addtime),count(huifu_zhutiid)
from table_1 a,table_2 b where a.zhuti_id=b.huifu_zhutiid group by huifu_zhutiid