declare @T table (开户类型 varchar(5),开始时间 datetime,结束时间 datetime)
insert into @T
select '类型1','2010-01-01','2010-10-15' union all
select '类型2','2010-10-20','2010-12-15' union all
select '类型3','2010-12-12','2011-01-01'

select * from @T

--假设今天是 2011-01-01
declare @i datetime set @i='2011-01-01'

------解决方案--------------------
SQL code

--创建一个函数
create function generateTimeV3
(
    @begin_date1 datetime,
    @end_date1 datetime,
    @begin_date2 datetime,
    @end_date2 datetime
)
returns int
as
begin
    declare @t1 table(date datetime)
    insert into @t1
    select dateadd(dd,number,@begin_date1) AS date 
    from master..spt_values 
    where type='p' and dateadd(dd,number,@begin_date1)<=@end_date1

    declare @t2 table(date datetime)
    insert into @t2
    select dateadd(dd,number,@begin_date2) AS date 
    from master..spt_values 
    where type='p' and dateadd(dd,number,@begin_date2)<=@end_date2
    declare @i int
    select @i =count(1) from @t1 a,@t2 b where a.date=b.date
    return @i
end
go

declare @T table (开户类型 varchar(5),开始时间 datetime,结束时间 datetime)
insert into @T
select '类型1','2010-01-01','2010-10-15' union all
select '类型2','2010-10-20','2010-12-15' union all
select '类型3','2010-12-12','2011-01-01'

--假设今天是 2011-01-01
declare @i datetime set @i='2011-01-01'

select dbo.generateTimeV3(开始时间,结束时间,dateadd(d,-30,@i),dateadd(d,-1,@i)) from @T 
/*
0
14
20
*/
select dbo.generateTimeV3(开始时间,结束时间,dateadd(d,-60,@i),dateadd(d,-31,@i)) from @T 
/*
0
30
0
*/
select dbo.generateTimeV3(开始时间,结束时间,dateadd(d,-90,@i),dateadd(d,-61,@i)) from @T 
/*
13
13
0
*/

--划分的时间段
select convert(varchar(10),dateadd(d,-30,@i),120),convert(varchar(10),dateadd(d,-1,@i),120)
union all
select convert(varchar(10),dateadd(d,-60,@i),120),convert(varchar(10),dateadd(d,-31,@i),120)
union all
select convert(varchar(10),dateadd(d,-90,@i),120),convert(varchar(10),dateadd(d,-61,@i),120)
/*
2010-12-02 2010-12-31
2010-11-02 2010-12-01
2010-10-03 2010-11-01
*/

------解决方案--------------------
SQL code

declare @T table (开户类型 varchar(5),开始时间 datetime,结束时间 datetime)
insert into @T
select '类型1','2010-01-01','2010-10-15' union all
select '类型2','2010-10-20','2010-12-15' union all
select '类型3','2010-12-12','2011-01-01'

--假设今天是 2011-01-01
declare @i datetime set @i='2011-01-01'

select c+ltrim(case when c1>30 then 30 else c1 end)+'天 逻辑说明（'+d1+'到'+d2+'）' from 
(
    select '0-30天使用时间：' as c,sum(dbo.generateTimeV3(开始时间,结束时间,dateadd(d,-30,@i),dateadd(d,-1,@i))) as c1,
    convert(varchar(10),dateadd(d,-30,@i),120)  as d1,convert(varchar(10),dateadd(d,-1,@i),120) as d2 from @T 
    union all
    select '30-60天使用时间：',sum(dbo.generateTimeV3(开始时间,结束时间,dateadd(d,-60,@i),dateadd(d,-31,@i))),
    convert(varchar(10),dateadd(d,-60,@i),120),convert(varchar(10),dateadd(d,-31,@i),120) from @T 
    union all
    select '60-90天使用时间：',sum(dbo.generateTimeV3(开始时间,结束时间,dateadd(d,-90,@i),dateadd(d,-61,@i))),
    convert(varchar(10),dateadd(d,-90,@i),120),convert(varchar(10),dateadd(d,-61,@i),120) from @T 
) aa

/* 运行结果：
0-30天使用时间：30天 逻辑说明（2010-12-02到2010-12-31）
30-60天使用时间：30天 逻辑说明（2010-11-02到2010-12-01）
60-90天使用时间：26天 逻辑说明（2010-10-03到2010-11-01）
*/

------解决方案--------------------
SQL code

if exists (select * from sysobjects where xtype='fn' and name='days')
  drop function days
go
c