create table tb(ID int,BH int,RS int)
insert into tb
 select 1,13,12 union 
 select 2,13,20 union 
 select 3,13,5

 select a.*,JG=row_number() over(order by id) 
  from tb a,master..spt_values 
   where type='P' and a.RS>number

/*
ID          BH          RS          JG
----------- ----------- ----------- -------
1           13          12          1
1           13          12          2
1           13          12          3
1           13          12          4
1           13          12          5
.......

------解决方案--------------------
探讨


SQL code
create table tb(ID int,BH int,RS int)
insert into tb
 select 1,13,12 union 
 select 2,13,20 union 
 select 3,13,5

 select a.*,JG=row_number() over(order by id) 
  from tb a,master..spt_val……


------解决方案--------------------
SQL code
--> 测试数据：[tb]
IF OBJECT_ID('[tb]') IS NOT NULL DROP TABLE [tb]
GO 
CREATE TABLE [tb]([ID] INT,[BH] INT,[RS] INT)
INSERT [tb]
SELECT 1,13,12 UNION ALL
SELECT 2,13,20 UNION ALL
SELECT 3,13,5
--------------开始查询--------------------------

SELECT a.*,ROW_NUMBER() OVER(ORDER BY GETDATE()) FROM [tb] AS a  
OUTER APPLY
    (
        SELECT number FROM master..spt_values WHERE type='p' AND number< [RS]
    ) AS opit
----------------结果----------------------------
/* 
ID    BH    RS    (无列名)
1    13    12    1
1    13    12    2
1    13    12    3
1    13    12    4
1    13    12    5
1    13    12    6
1    13    12    7
1    13    12    8
1    13    12    9
1    13    12    10
1    13    12    11
1    13    12    12
2    13    20    13
2    13    20    14
2    13    20    15
2    13    20    16
2    13    20    17
2    13    20    18
2    13    20    19
2    13    20    20
2    13    20    21
2    13    20    22
2    13    20    23
2    13    20    24
2    13    20    25
2    13    20    26
2    13    20    27
2    13    20    28
2    13    20    29
2    13    20    30
2    13    20    31
2    13    20    32
3    13    5    33
3    13    5    34
3    13    5    35
3    13    5    36
3    13    5    37
*/