table1 name createdate a 2011-03-01 10:00:00 a 2011-03-01 11:00:00 a 2011-03-01 14:00:00 b 2011-03-01 13:00:00 b 2011-03-01 13:20:00 b 2011-03-01 14:00:00 查询结果为 name createdate count a 2011-03-01 10:00:00 2 a 2011-03-01 14:00:00 1 b 2011-03-01 13:00:00 3 就相当于是统计name字段中的值在第一次出现后的2小时内，总共出现了几次？
这个是网上的解答：
declare @table1 table(name nvarchar,createdate smalldatetime)
insert into @table1
select 'a','2011-03-01 10:00:00'
union all select 'a','2011-03-01 11:00:00'
union all select 'a','2011-03-01 14:00:00'
union all select 'b','2011-03-01 13:00:00'
union all select 'b','2011-03-01 13:20:00'
union all select 'b','2011-03-01 14:00:00'
select name,
createdate,
(select count(createdate)
from @table1 b
where a.name=b.name and
a.createdate<=b.createdate and
dateadd(hh,2,a.createdate) >= b.createdate
) as count
from @table1 a
where not exists
(select 1 from
@table1 b
where a.name=b.name and
a.createdate>b.createdate and
a.createdate<dateadd(hh,2,b.createdate))
group by name,createdate
但是这个解答其实是有问题的，当把临时表中的第3条数据的createdate改为'2011-03-01 12:00:00'，那么显示的结果是：
name createdate count
a 2011-03-01 10:00:00 3
b 2011-03-01 13:00:00 3
在其中没有包括createdate为'2011-03-01 12:00:00'的记录，因为这个时间到为'2011-03-01 10:00:00'是超过2个小时了，也就是说为'2011-03-01 10:00:00'是第一个出现时间，到为'2011-03-01 11:59:59'为止，接下来应该是从'2011-03-01 12:00:00'开始的下个区间了，而这里显然是有问题的。
以下是我写的解法，虽然效率不是太高，但是能解决这个问题：
declare @table1 table(name nvarchar,createdate smalldatetime)
insert into @table1
select 'a','2011-03-01 10:00:00'
union all select 'a','2011-03-01 11:00:00'
union all select 'a','2011-03-01 12:00:00'
union all select 'b','2011-03-01 13:10:00'
union all select 'b','2011-03-01 13:20:00'
union all select 'b','2011-03-01 14:30:00'
union all select 'b','2011-03-01 15:15:00'
union all select 'b','2011-03-01 16:00:00'
union all select 'b','2011-03-01 17:00:00'
;with aa --按照name分区，同时按照createdate排序编号
as
(
select name,
createdate,
ROW_NUMBER() over(partition by name
order by createdate) as k1
from @table1
),
r
as
(
select v.name,
starts=v.k1, --区间开始的编号
ends=isnull(
min(case when v.k1<a.k1
and DATEADD(hour,2,v.createdate) <= a.createdate
then a.k1
else null
end)-1,
max(case when v.k1<a.k1
then a.k1
else v.k1
end)
), --区间结尾的编号
isnull(
min(case when v.k1<a.k1
and DATEADD(hour,2,v.createdate) <= a.createdate
then a.k1
else null
end)-1,
max(case when v.k1<a.k1
then a.k1
else v.k1
end)
) - v.k1 as diff --区间结尾编号与区间开始编号之间的差值
from aa v
inner join aa a
on v.name = a.name --只关联name相等的
group by v.name,
v.k1
having isnull(
min(case when v.k1<a.k1
and DATEADD(hour,2,v.createdate) <= a.createdate
then a.k1
else null
end)-1,
max(case when v.k1<a.k1
then a.k1
else v.k1
end)
) >=v.k1
and
isnull(
max(case when v.k1>a.k1 and
DATEADD(hour,-2,v.createdate) >= a.createdate
then v.k1 - 1
else null
end) + 1,
min(case when v.k1>a.k1
then a.k1
else v.k1
end)
) = v.k1
)
--select * from r
select aa.name,
aa.createdate,
diff + 1
from r
inner join aa
on aa.name = r.name
and aa.k1 =r.starts
where not exists
(select 1
from r rr
where rr.name = r.name and
rr.starts <> r.starts and
rr.starts < r.starts and
(rr.ends = r.ends or
rr.ends = r.starts)
)
不过发现我的这个解法也是有问题的，最大的问题在与不能准确的确定上限在那里，还得继续考虑问题的解法。
下面这个也是有问题的：
declare @table1 table(name nvarchar,createdate smalldatetime)
insert into @table1
select 'a','2011-03-01 10:00:00'
union all select 'a','2011-03-01 11:00:00'
union all select 'a','2011-03-01 12:00:00'
--union all select 'b','2011-03-01 13:10:00'
--union all select 'b','2011-03-01 13:20:00'
--union all select 'b','2011-03-01 14:30:00'
--union all select 'b','2011-03-01 15:15:00'
--union all select 'b','2011-03-01 16:00:00'
--union all select 'b','2011-03-01 17:15:00'
;with a --按照name分区，同时按照createdate排序编号
as
(
select name,
createdate,
ROW_NUMBER() over(partition by name
order by createdate) as k1
from @table1
),
c
as
(
select a1.name,
a1.createdate,
a1.k1,
MIN(a2.createdate) as nextCreatedate,
MIN(a2.k1) as nextK1
from a a1
inner join a a2
on a1.name = a2.name
and a2.createdate < DATEADD(hour,2,a1.createdate)
and a2.createdate >= a1.createdate
and a1.k1 <= a2.k1
group by a1.name,
a1.createdate,
a1.k1
),
w
as
(
select name,
createdate,
k1
--null,
--null,
--null
from a
where k1 = 1
union all
select c.name,
c.nextCreatedate,
c.nextK1
from W
inner join a
on a.name = w.name
and dateadd(hour,2,w.createdate) <= a.createdate
and w.k1 <= a.k1
and w.createdate <> '2011-03-01 12:00:00'
inner join c
on w.name = c.name
and w.createdate = c.createdate
and w.k1 = c.k1
where w.k1 <=3
)
SELECT *
FROM w
下面的解法是正确的，不过用的是T-SQL，不是纯sql了：
declare @table1 table(name nvarchar(100),createdate smalldatetime)
declare @table2 table(name nvarchar(100),createdate smalldatetime,rnum bigint)
declare @temp table(name nvarchar(100),createdate smalldatetime,rnum bigint)
declare @i int = 1;
insert into @table1
select 'a','2011-03-01 10:00:00'
union all select 'a','2011-03-01 11:00:00'
union all select 'a','2011-03-01 12:00:00'
union all select 'b','2011-03-01 13:10:00'
union all select 'b','2011-03-01 13:20:00'
union all select 'b','2011-03-01 14:30:00'
union all select 'b','2011-03-01 15:15:00'
union all select 'b','2011-03-01 16:00:00'
union all select 'b','2011-03-01 17:16:00'
union all select 'b','2011-03-01 17:15:00'
;with a --按照name分区，同时按照createdate排序编号
as
(
select name,
createdate,
ROW_NUMBER() over(partition by name
order by createdate) as k1
from @table1
)
insert into @table2
select * from a
insert into @temp
select name,
createdate,
rnum
from @table2
where rnum = 1
--select * from @temp
while @i <= (select MAX(rnum) from @table2)
begin
insert into @temp
select t2.name,
min(t2.createdate),
@i +1
from @temp t1
inner join @table2 t2
on t1.name = t2.name
and t2.createdate >= dateadd(hour,2,t1.createdate)
where t1.rnum = @i
group by t2.name
set @i = @i + 1
end
;with r
as
(
select name,
createdate
from @temp
group by name,
createdate
)
select r.name,
r.createdate,
COUNT(1)
from r
inner join @table1 t
on t.name = r.name
and t.createdate >= r.createdate
and t.createdate <DATEADD(HOUR,2,r.createdate)
group by r.name,
r.createdate
其实这个问题是个递归问题，由上一个找到下一个，但是得构造一下：
declare @table1 table(name nvarchar,createdate smalldatetime)
insert into @table1
select 'a','2011-03-01 10:00:00'
union all select 'a','2011-03-01 11:00:00'
union all select 'a','2011-03-01 12:00:00'
union all select 'a','2011-03-01 12:20:00'
union all select 'b','2011-03-01 13:10:00'
union all select 'b','2011-03-01 13:20:00'
union all select 'b','2011-03-01 14:30:00'
union all select 'b','2011-03-01 15:15:00'
union all select 'b','2011-03-01 16:00:00'
union all select 'b','2011-03-01 17:20:00'
union all select 'b','2011-03-01 17:15:00'
union all select 'b','2011-03-01 19:16:00'
union all select 'b','2011-03-01 17:15:00'
;with a --按照name分区，同时按照createdate排序编号
as
(
select name,
createdate,
ROW_NUMBER() over(partition by name
order by createdate) as k1
from @table1
),
c --对于每个时间,找到大于这个时间2小时的时间中最小那个时间
as
(
select a1.name,
a1.createdate,
a1.k1,
MIN(a2.createdate) as nextCreatedate,
MIN(a2.k1) as nextK1
from a a1
inner join a a2
on a1.name = a2.name
and a2.createdate >= DATEADD(hour,2,a1.createdate)
group by a1.name,
a1.createdate,
a1.k1
union all
select a.name,null,null,a.createdate,1 --构造递归运行时需要的层级
from a
where k1 = 1
),
w --递归查询
as
(
select c.name,
c.createdate,
c.k1,
c.nextCreatedate,
c.nextK1,
1 as lev
from c
where createdate is null
and k1 is null
union all
select c.name,
c.createdate,
c.k1,
c.nextCreatedate,
c.nextK1,
lev + 1
from W
inner join c
on w.name = c.name
and w.nextCreatedate = c.createdate
)
SELECT distinct name,
nextCreatedate,
nextK1
FROM w