怎样在一个时间段内记录,只取最早的一条记录?

表:

工号        日期
--------------------------------
12006-03-15 08:00:40.000
12006-03-15 18:10:35.000
12006-03-15 18:10:36.000
22006-03-15 07:54:45.000
22006-03-15 18:10:03.000
32006-03-15 07:59:46.000
32006-03-15 07:59:47.000
32006-03-15 19:15:30.000
42006-03-15 08:03:47.000
42006-03-15 19:41:08.000
52006-03-15 19:41:09.000

结果(同一工号日期在5分钟范围内的记录,只取最早的一条记录):
工号        日期
---------------------------------
12006-03-15 08:00:40.000
12006-03-15 18:10:35.000
22006-03-15 07:54:45.000
22006-03-15 18:10:03.000
32006-03-15 07:59:46.000
32006-03-15 19:15:30.000
42006-03-15 08:03:47.000
42006-03-15 19:41:08.000
52006-03-15 19:41:09.000

declare @tbl table (工号 int,日期 datetime)
insert into @tbl
select 1,'2006-03-15 08:00:40.000'
union select 1,'2006-03-15 18:10:35.000'
union select 1,'2006-03-15 18:10:36.000'
union select 2,'2006-03-15 07:54:45.000'
union select 2,'2006-03-15 18:10:03.000'
union select 3,'2006-03-15 07:59:46.000'
union select 3,'2006-03-15 07:59:47.000'
union select 3,'2006-03-15 19:15:30.000'
union select 4,'2006-03-15 08:03:47.000'
union select 4,'2006-03-15 19:41:08.000'
union select 5,'2006-03-15 19:41:09.000'

select * from @tbl as a
where not exists(
  select * from @tbl where 工号=a.工号 and
     abs(datediff(Second,日期,a.日期))<=300 and a.日期<日期)

declare @tbl table (工号 int,日期 datetime)
insert into @tbl
      select 1,'2006-03-15 08:00:40.000'
union select 1,'2006-03-15 18:10:35.000'
union select 1,'2006-03-15 18:10:36.000'
union select 2,'2006-03-15 07:54:45.000'
union select 2,'2006-03-15 18:10:03.000'
union select 3,'2006-03-15 07:59:46.000'
union select 3,'2006-03-15 07:59:47.000'
union select 3,'2006-03-15 19:15:30.000'
union select 4,'2006-03-15 08:03:47.000'
union select 4,'2006-03-15 19:41:08.000'
union select 5,'2006-03-15 19:41:09.000'

select distinct a.*
from
    @tbl a
where
    not exists(select
                   1
               from
                   @tbl
               where
                   工号=a.工号
                   and
                   (datediff(ss,日期,a.日期) between 1 and 300))

 

 

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