create table tb
(
  [type] varchar(10),
  startdate datetime,
  enddate datetime,
  counttime decimal(5,1),
  id int identity(1,1)
)


insert into tb 
select '1', '2012-04-18 14:33:22.640', '2012-04-21 14:33:22.640', 3.0 union all
select '1', '2012-04-14 14:34:48.970', '2012-04-17 14:34:48.970', 3.0 union all
select '2', '2012-04-19 14:34:49.407', '2012-04-21 14:34:49.407', 2.0 union all
select '2', '2012-04-23 14:34:50.220', '2012-04-24 14:34:50.220', 1.0

select t1.加班时间 ,t2.调休时间 ,t1.加班时间 -t2.调休时间 AS 结余数 from
(select [type],SUM(counttime) AS 加班时间 from tb where [type]='1' group by [type]) t1,
(select [type],SUM(counttime) AS 调休时间 from tb where [type]='2' group by [type]) t2

------解决方案--------------------

SQL code

--> 测试数据：[test]
if object_id('[test]') is not null drop table [test]
create table [test](
[type] int,
[startdate] datetime,
[enddate] datetime,
[counttime] numeric(2,1),
[id] int
)
insert [test]
select 1,'2012-04-18 14:33:22.640','2012-04-21 14:33:22.640',3.0,1 union all
select 1,'2012-04-14 14:34:48.970','2012-04-17 14:34:48.970',3.0,2 union all
select 2,'2012-04-19 14:34:49.407','2012-04-21 14:34:49.407',2.0,3 union all
select 2,'2012-04-23 14:34:50.220','2012-04-24 14:34:50.220',1.0,4

select 加班总时数,调休总时数,调休总时数-加班总时数 as 本月结余 from(
select 
SUM(case when [type]=1 then [counttime] else 0 end) as 加班总时数,
SUM(case when [type]=2 then [counttime] else 0 end) as 调休总时数
from test)a
/*
加班总时数    调休总时数    本月结余
6.0    3.0    -3.0
*/