SQL计数连续的行

Question

我在表中有以下数据:

|event_id    |starttime        |person_id|attended|
|------------|-----------------|---------|--------|
| 11512997-1 | 01-SEP-16 08:00 | 10001   | N      |
| 11512997-2 | 01-SEP-16 10:00 | 10001   | N      |
| 11512997-3 | 01-SEP-16 12:00 | 10001   | N      |
| 11512997-4 | 01-SEP-16 14:00 | 10001   | N      |
| 11512997-5 | 01-SEP-16 16:00 | 10001   | N      |
| 11512997-6 | 01-SEP-16 18:00 | 10001   | Y      |
| 11512997-7 | 02-SEP-16 08:00 | 10001   | N      |
| 11512997-1 | 01-SEP-16 08:00 | 10002   | N      |
| 11512997-2 | 01-SEP-16 10:00 | 10002   | N      |
| 11512997-3 | 01-SEP-16 12:00 | 10002   | N      |
| 11512997-4 | 01-SEP-16 14:00 | 10002   | Y      |
| 11512997-5 | 01-SEP-16 16:00 | 10002   | N      |
| 11512997-6 | 01-SEP-16 18:00 | 10002   | Y      |
| 11512997-7 | 02-SEP-16 08:00 | 10002   | Y      |

我想生成以下结果,其中返回atended ='N'的最大连续出现次数:

|person_id|consec_missed_max|
| 1001    | 5               |
| 1002    | 3               |

如何在Oracle(或ANSI)SQL中完成此操作？谢谢!

编辑:

到目前为止,我尝试过:

WITH t1 AS
(SELECT t.person_id,
    row_number() over(PARTITION BY t.person_id ORDER BY t.starttime) AS idx
    FROM the_table t
    WHERE t.attended = 'N'),
t2 AS
(SELECT person_id, MAX(idx) max_idx FROM t1 GROUP BY person_id)
SELECT t1.person_id, COUNT(1) ct
    FROM t1
    JOIN t2
    ON t1.person_id = t2.person_id
GROUP BY t1.person_id;

Answer 1

主要工作在因子子查询"准备"中.您似乎对分析功能有点熟悉,但这还不够.该解决方案使用所谓的"tabibitosan"方法在一个或多个维度中创建具有相同特征的连续行组; 在这种情况下,您希望将每个序列的连续N行分组为不同的组.这是通过两个ROW_NUMBER()调用的差异来完成的 - 一个是按人员划分的,另一个是按人划分并参加.谷歌"tabibitosan"如果需要,可以阅读更多关于这个想法的内容.

with
     inputs ( event_id, starttime, person_id, attended ) as (
        select '11512997-1', to_date('01-SEP-16 08:00', 'dd-MON-yy hh24:mi'), 10001, 'N' from dual union all
        select '11512997-2', to_date('01-SEP-16 10:00', 'dd-MON-yy hh24:mi'), 10001, 'N' from dual union all     
        select '11512997-3', to_date('01-SEP-16 12:00', 'dd-MON-yy hh24:mi'), 10001, 'N' from dual union all
        select '11512997-4', to_date('01-SEP-16 14:00', 'dd-MON-yy hh24:mi'), 10001, 'N' from dual union all
        select '11512997-5', to_date('01-SEP-16 16:00', 'dd-MON-yy hh24:mi'), 10001, 'N' from dual union all
        select '11512997-6', to_date('01-SEP-16 18:00', 'dd-MON-yy hh24:mi'), 10001, 'Y' from dual union all
        select '11512997-7', to_date('02-SEP-16 08:00', 'dd-MON-yy hh24:mi'), 10001, 'N' from dual union all
        select '11512997-1', to_date('01-SEP-16 08:00', 'dd-MON-yy hh24:mi'), 10002, 'N' from dual union all
        select '11512997-2', to_date('01-SEP-16 10:00', 'dd-MON-yy hh24:mi'), 10002, 'N' from dual union all
        select '11512997-3', to_date('01-SEP-16 12:00', 'dd-MON-yy hh24:mi'), 10002, 'N' from dual union all
        select '11512997-4', to_date('01-SEP-16 14:00', 'dd-MON-yy hh24:mi'), 10002, 'Y' from dual union all
        select '11512997-5', to_date('01-SEP-16 16:00', 'dd-MON-yy hh24:mi'), 10002, 'N' from dual union all
        select '11512997-6', to_date('01-SEP-16 18:00', 'dd-MON-yy hh24:mi'), 10002, 'Y' from dual union all
        select '11512997-7', to_date('02-SEP-16 08:00', 'dd-MON-yy hh24:mi'), 10002, 'Y' from dual
      ),
      prep ( starttime, person_id, attended, gp ) as (
        select starttime, person_id, attended,
               row_number() over (partition by person_id order by starttime) -
                   row_number() over (partition by person_id, attended 
                                      order by starttime)
        from   inputs
      ),
      counts ( person_id, consecutive_absences ) as (
        select person_id, count(*)
        from   prep
        where  attended = 'N'
        group by person_id, gp
     )
select person_id, max(consecutive_absences) as max_consecutive_absences
from   counts
group by person_id
order by person_id;

OUTPUT:

 PERSON_ID                MAX_CONSECUTIVE_ABSENCES
---------- ---------------------------------------
     10001                                       5
     10002                                       3