求写法解决思路_Sql Server

求写法
描述：
tb中有一个字段
类别
a
a
b
b
b
c
c
现在想加个字段形成如下内容
类别排序
a 0001
a 0002
b 0001
b 0002
b 0003
c 0001
c 0002
请问我该怎么弄，直接在企业管理器设计字段能实现最好

------解决方案--------------------

SQL code

declare @tab table(    V nvarchar(2))insert into @tab(v)select 'a' union allselect 'a' union allselect 'b' union allselect 'b' union allselect 'b' union allselect 'c' union allselect 'c' select V,right('0000'+convert(nvarchar(4),row_number() over(partition by V order by V)),4) from @taba    0001a    0002b    0001b    0002b    0003c    0001c    0002
------解决方案--------------------
SQL codecreate table tb(类别 char(2))insert into tb(类别)select 'a' union all select 'a' union all select 'b' union all select 'b' union all select 'b' union all select 'c' union all select 'c'select 类别,'000'+cast(row_number() over(partition by 类别 order by getdate()) as varchar) '排序'from tb类别   排序---- ---------------------------------a    0001a    0002b    0001b    0002b    0003c    0001c    0002(7 row(s) affected)