求助，我想在查找出来的结果集中指定行加空行，怎么办？

[ccpud]

比如数据库数据是这样的
a b
22 11
22 31
22 21
34 22
23 32
23 23
23 12
34 13
a列是组号，b列的号是唯一的。我想要的效果是，a列值相等的放到一起，然后空一格，再放下一组的数据。
比如
22 11
22 21
22 31

23 32
23 12
23 23

34 22
34 13

另外一个问题。a列是组号，我想要的效果是，b列有Z个值，我就从1到Z给它分好。
比如
22 11 1
22 21 2
22 31 3

23 32 1
23 12 2
23 23 3

34 22 1
34 13 2

每组都从1开始。

[dawugui]

select t.* , row_number() over(partition by a order by b) from tb t

[Oraclefans_]

--------这样可以不
SQL> with tab as
  2  (
  3  select 22 a, 11 b from dual union all
  4  select 22 a, 31 b from dual union all
  5  select 22 a, 21 b from dual union all
  6  select 34 a, 22 b from dual union all
  7  select 23 a, 32 b from dual union all
  8  select 23 a, 23 b from dual union all
  9  select 23 a, 12 b from dual union all
 10  select 34 a, 13 b from dual
 11  )
 12  select decode(b, null, '-----------', a) a,
 13         decode(b, null, '-----------', b),
 14         decode(b, null, '-----------', rn) rn
 15    from (select a, b, row_number() over(partition by a order by b) rn
 16            from tab
 17           group by rollup(a, b))
 18  ;

A                                        DECODE(B,NULL,'-----------',B)           RN
---------------------------------------- ---------------------------------------- ----------------------------------------
22                                       11                                       1
22                                       21                                       2
22                                       31                                       3
-----------                              -----------                              -----------
23                                       12                                       1
23                                       23                                       2
23                                       32                                       3
-----------                              -----------                              -----------
34                                       13                                       1
34                                       22                                       2
-----------                              -----------                              -----------
-----------                              -----------                              -----------

12 rows selected

SQL> 

[Phoenix_99]

第一个：

with temp as(
select 22 a,11 b from dual
union all
select 22 a,31 b from dual
union all
select 22 a,21 b from dual
union all
select 34 a,22 b from dual
union all
select 23 a,32 b from dual
union all
select 23 a,23 b from dual
union all
select 23 a,12 b from dual
union all
select 34 a,13 b from dual
)
select case when b is null then null else a end a,b from(
select a,b,max(a) c from(
select a, b  from temp
union all
select a,null b from temp group by a
) group by a,b
) order by c,a

第二个：

select t.* , row_number() over(partition by a order by b) from tb t

[ccpud]

谢谢Oraclefans_。也谢谢爱新觉罗.毓华和Phoenix_99。因为发帖比较急，给的分不多，所以全给Oraclefans_了。再次感谢各位