选择单列时差小于 2 小时的行

Question

表：测试

选择同一天时差小于 2 小时的行（按日期分组）。

这里输出应该是前两行，因为前两行的时间差（18-JAN-15 01.08.40.000000000 PM - 18-JAN-15 11.21.28.000000000 AM < 2 小时）

NB: compare rows of same date.

输出：

  CREATE TABLE TEST
  ( "ID" VARCHAR2(20 BYTE), 
    "CAM_TIME" TIMESTAMP (6)
  ) 

Insert into TEST (ID,CAM_TIME) values ('1',to_timestamp('18-JAN-15 11.21.28.000000000 AM','DD-MON-RR HH.MI.SSXFF AM'));
Insert into TEST (ID,CAM_TIME) values ('2',to_timestamp('18-JAN-15 01.08.40.000000000 PM','DD-MON-RR HH.MI.SSXFF AM'));

Insert into TEST (ID,CAM_TIME) values ('3',to_timestamp('23-JAN-15 09.18.40.000000000 AM','DD-MON-RR HH.MI.SSXFF AM'));
Insert into TEST (ID,CAM_TIME) values ('4',to_timestamp('23-JAN-15 04.22.22.000000000 PM','DD-MON-RR HH.MI.SSXFF AM'));

Answer 1

这个自连接查询完成以下工作：

SQL小提琴

select distinct t1.id, t1.cam_time 
  from test t1 join test t2 on t1.rowid <> t2.rowid  
    and trunc(t1.cam_time) = trunc(t2.cam_time)
  where abs(t1.cam_time-t2.cam_time) <= 2/24
  order by t1.id

编辑：

如果 cam_time 是 time_stamp 类型，那么条件应该是：

where t1.cam_time between t2.cam_time - interval '2' Hour 
                      and t2.cam_time + interval '2' Hour

Answer 2

我采取了稍微不同的策略并使用了LAG()和LEAD()分析函数：

WITH mydata AS (
  SELECT 1 AS id, timestamp '2015-01-15 11:21:28.000' AS cam_time
    FROM dual
   UNION ALL
  SELECT 2 AS id, timestamp '2015-01-15 13:08:40.000' AS cam_time
    FROM dual
   UNION ALL
  SELECT 3 AS id, timestamp '2015-01-23 09:18:40.000' AS cam_time
    FROM dual
   UNION ALL
  SELECT 4 AS id, timestamp '2015-01-23 16:22:22.000' AS cam_time
    FROM dual
)
SELECT id, cam_time FROM (
    SELECT id, cam_time
         , LAG(cam_time) OVER ( PARTITION BY TRUNC(cam_time) ORDER BY cam_time ) AS lag_time
         , LEAD(cam_time) OVER ( PARTITION BY TRUNC(cam_time) ORDER BY cam_time ) AS lead_time
      FROM mydata
) WHERE CAST(lead_time AS DATE) - CAST(cam_time AS DATE) < 1/12
     OR CAST(cam_time AS DATE) - CAST(lag_time AS DATE) < 1/12