关于外连接的简单有关问题

关于外连接的简单问题
表A 表B
ID ANUM ID BNUM
1 10 1 10
2 10 2 10
3 10 4 10
希望得出结果
ID ANUM BNUM
1 10 10
2 10 10
3 10
4 10

用语句 SELECT a.id, anum, bnum from a full outer join b on a.id= b.id
得出的结果是 
1 10 10
2 10 10
3 10
  10

这个问题应该怎么修正? 急 谢谢指教

[解决办法]
try it ..

id(a)->aid, id(b)->bid

SQL code

SQL:select tt.sid,       max(tt.anum) as anum,       max(tt.bnum) as bnum  from (        select a.aid as sid,              a.anum,              null as bnum         from A        union        select b.bid as sid,              null as anum,              b.bnum         from B        )tt group by tt.sid;RESULT:       SID       ANUM       BNUM---------- ---------- ----------         1         10         10         2         10         10         3         10          4                    10