大过年的，求助oracle问题
这个是我写的sql语句
select count(考勤天数),员工ID，月份 from 考勤表 group by 员工ID，月份；
下边这个是查询出来的结果：
考勤天数 员工ID 月份
28 A 4
26 A 3
25 A 2
28 B 3
26 B 2
27 C 4
30 C 3
27 C 2
我想让它查询出这样的显示结果怎么做呢？
员工ID 4月 3月 2月
A 28 26 25
B 0 28 26
C 27 30 27
要用oracle中的sql实现，亲们，没人帮就回不去了。 
[解决办法]
--sql
with T
as
(select 28 a , 'A' b , 4 c from dual
union all
select 26 , 'A' , 3 from dual
union all
select 25 , 'A' , 2 from dual
union all
select 28 , 'B' , 3 from dual
union all
select 26 , 'B' , 2 from dual
union all
select 27 , 'C' , 4 from dual
union all
select 30 , 'C' , 3 from dual
union all
select 27 , 'C' , 2 from dual
)
select b,sum(case when c=4 then a else 0 end) as April,
sum(case when c=3 then a else 0 end) as March,
sum(case when c=2 then a else 0 end) as Feb
from t group by b
--result:
A282625
B02826
C273027
[解决办法]
select b,max(decode(c,4,a,0)) as April,max(decode(c,3,a,0)) as March,max(decode(c,2,a,0)) as Feb
from t group by b
--11g
SELECT * FROM t PIVOT(sum(a) FOR c IN (4 as April, 3 as March, 2 as Feb))
[解决办法]
先依据每个员工的id进行行列转换，把月份的值由行转换为列，需要用到case when 语句。然后再依据每个员工id，进行group by，这就行了。具体的做法就像1楼一样。
[解决办法]
SAMPLE:
create table test (times number, months number, emp varchar2(20));
--drop table test;
insert into test values(28,2,'A');
insert into test values(29,3,'A');
insert into test values(30,4,'A');
insert into test values(31,3,'B');
insert into test values(29,4,'B');
insert into test values(26,2,'C');
insert into test values(30,3,'C');
insert into test values(27,4,'C');
SELECT * FROM TEST;
TIMESMONTHSEMP
1282A
2293A
3304A
4313B
5294B
6262C
7303C
8274C
select EMP, SUM(DECODE(MONTHS, 2, TIMES, 0)) AS FEB
,SUM(DECODE(MONTHS, 3, TIMES, 0)) AS MARCH
,SUM(DECODE(MONTHS, 4, TIMES, 0)) AS APRIL from test GROUP BY EMP;
EMPFEBMARCHAPRIL
1A282930
2B03129
3C263027