请问这条SQL语句应该怎么写?
现有一个表,   结构和数据如下:

A       B       C
1       2       S1
1       2       S3
1       2       S2

其中A和B列为数字类型,   C为字符串类型,   且C列的值只有S1,S2,S3三个,   A列的值只为1,   B列的值只为2,   现在我想把表的结构调整一下,   显示如下:
A       B       C1       C2       C3
1       2       S1       S2       S3

请问这条SQL语句应该怎么写?     谢谢.

------解决方案--------------------
create table T(A int, B int, C varchar(10))
insert T select 1, 2, 'S1 '
union all select 1, 2, 'S3 '
union all select 1, 2, 'S2 '

select A, B,
C1=max(case when C= 'S1 ' then C end),
C2=max(case when C= 'S2 ' then C end),
C3=max(case when C= 'S3 ' then C end)
from T
group by A, B

--result
A B C1 C2 C3
----------- ----------- ---------- ---------- ----------
1 2 S1 S2 S3

(1 row(s) affected)
------解决方案--------------------
create table T(A int, B int, C varchar(10))
insert T select 1, 2, 'S1 '
union all select 1, 2, 'S3 '
union all select 1, 2, 'S2 '

insert into t values(2,3, 's1 ')
insert into t values(2,2, 's2 ')


declare @table varchar(5000)
set @table = 'select a,b, '
select @table=@table+ '(select c from t bb where bb.c= '+QUOTENAME(c, ' ' ' ')+
' and bb.a=aa.a and bb.b=aa.b) '+QUOTENAME(c)+ ', '
from t group by c
set @table = left(@table,len(@table)-1)+ 'from t aa group by a,b '
exec (@table)