我正在尝试在我的测量数据中建立一组降水事件。我有一个时间，一个测量值和一个标志，注意到它是否在下雨：
00:00, 32.4, 0
00:10, 32.4, 0
00:20, 32.6, 1
00:30, 32.7, 1
00:40, 32.9, 1
00:50, 33.2, 1
01:00, 33.2, 0
01:10, 33.2, 0
01:20, 33.2, 0
01:30, 33.5, 1
01:40, 33.6, 1
01:50, 33.6, 0
02:00, 33.6, 0
...
现在我想为降水事件生成事件ID：
00:00, 32.4, 0, NULL
00:10, 32.4, 0, NULL
00:20, 32.6, 1, 1
00:30, 32.7, 1, 1
00:40, 32.9, 1, 1
00:50, 33.2, 1, 1
01:00, 33.2, 0, NULL
01:10, 33.2, 0, NULL
01:20, 33.2, 0, NULL
01:30, 33.5, 1, 2
01:40, 33.6, 1, 2
01:50, 33.6, 0, NULL
02:00, 33.6, 0, NULL
...
然后我将能够使用分组来总结事件。任何提示如何在Oracle中执行此操作都非常感谢。
到目前为止，我能够计算出上面提到的标志和最后一行的差异：
SELECT
measured_at,
station_id
ps, -- precipitation sum
ps - lag(ps, 1, NULL) OVER (ORDER BY measured_at ASC) as p, -- precipitation delta
CASE
WHEN ps - lag(ps, 1, NULL) OVER (ORDER BY measured_at ASC) > 0 THEN 1
ELSE 0
END as rainflag
FROM measurements;
我认为必须以某种方式生成所需的事件ID，但无法弄明白。谢谢你的时间！
DROP TABLE events;
CREATE TABLE events (measured_at, station_id, ps) AS
SELECT TO_DATE('2016-05-01 12:00', 'YYYY-MM-DD HH24:MI'), 'XYZ', 32.4 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 12:10', 'YYYY-MM-DD HH24:MI'), 'XYZ', 32.6 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 12:20', 'YYYY-MM-DD HH24:MI'), 'XYZ', 32.7 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 12:30', 'YYYY-MM-DD HH24:MI'), 'XYZ', 32.9 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 12:40', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.2 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 12:50', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.2 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 13:00', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.2 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 13:10', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.2 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 13:20', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.5 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 13:30', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.6 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 13:40', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.6 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 13:50', 'YYYY-MM-DD HH24:MI'), 'XYZ', 33.5 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 17:00', 'YYYY-MM-DD HH24:MI'), 'XYZ', 39.1 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 17:10', 'YYYY-MM-DD HH24:MI'), 'XYZ', 39.2 FROM DUAL UNION ALL
SELECT TO_DATE('2016-05-01 17:20', 'YYYY-MM-DD HH24:MI'), 'XYZ', 39.2 FROM DUAL;
WITH
flagged AS (
SELECT
measured_at,
station_id,
ps,
CASE
WHEN measured_at - lag(measured_at, 1, NULL) OVER (ORDER BY measured_at) = (1/144) THEN ps - lag(ps, 1, NULL) OVER (ORDER BY measured_at)
ELSE NULL
END as delta_p,
CASE
WHEN ps - lag(ps, 1, NULL) OVER (ORDER BY measured_at) > 0 THEN 1
ELSE 0
END AS rain
FROM events
),
eventmarked AS (
SELECT
f.*,
CASE
WHEN f.delta_p >= 0 THEN f.delta_p
ELSE NULL
END AS p,
CASE rain
WHEN 1 THEN COUNT(1) OVER (ORDER BY measured_at) - SUM(rain) OVER (ORDER BY measured_at)
END as event
FROM flagged f
),
summarized AS (
SELECT
em.*,
sum(CASE p WHEN 0 THEN NULL ELSE p END) OVER (PARTITION BY event ORDER BY measured_at) as e_ps
FROM eventmarked em
)
SELECT measured_at, station_id, ps, p, e_ps FROM summarized
ORDER BY measured_at;
答案 0 :(得分：2)
Oracle安装程序：
CREATE TABLE events ( measured_at, station_id, ps ) AS
SELECT '00:00', 32.4, 0 FROM DUAL UNION ALL
SELECT '00:10', 32.4, 0 FROM DUAL UNION ALL
SELECT '00:20', 32.6, 1 FROM DUAL UNION ALL
SELECT '00:30', 32.7, 1 FROM DUAL UNION ALL
SELECT '00:40', 32.9, 1 FROM DUAL UNION ALL
SELECT '00:50', 33.2, 1 FROM DUAL UNION ALL
SELECT '01:00', 33.2, 0 FROM DUAL UNION ALL
SELECT '01:10', 33.2, 0 FROM DUAL UNION ALL
SELECT '01:20', 33.2, 0 FROM DUAL UNION ALL
SELECT '01:30', 33.5, 1 FROM DUAL UNION ALL
SELECT '01:40', 33.6, 1 FROM DUAL UNION ALL
SELECT '01:50', 33.6, 0 FROM DUAL UNION ALL
SELECT '02:00', 33.6, 0 FROM DUAL;
<强>查询：
SELECT measured_at,
station_id,
ps,
CASE WHEN rainflag IS NOT NULL THEN DENSE_RANK() OVER ( ORDER BY rainflag ) END AS rainflag
FROM (
SELECT e.*,
CASE ps
WHEN 1
THEN COUNT( 1 ) OVER ( ORDER BY measured_at )
- SUM( ps ) OVER ( ORDER BY measured_at )
END AS rainflag
FROM events e
)
ORDER BY measured_at;
查询2
SELECT measured_at,
station_id,
ps,
CASE ps WHEN 1
THEN SUM( rainflag ) OVER ( ORDER BY measured_at )
END AS rainflag
FROM (
SELECT e.*,
CASE WHEN ps > LAG( ps, 1, 0 ) OVER ( ORDER BY measured_at )
THEN 1
END AS rainflag
FROM events e
);
<强>输出：
MEASURED_AT STATION_ID PS RAINFLAG
----------- ---------- ---------- ----------
00:00 32.4 0
00:10 32.4 0
00:20 32.6 1 1
00:30 32.7 1 1
00:40 32.9 1 1
00:50 33.2 1 1
01:00 33.2 0
01:10 33.2 0
01:20 33.2 0
01:30 33.5 1 2
01:40 33.6 1 2
01:50 33.6 0
02:00 33.6 0
答案 1 :(得分：1)
仅使用LAG函数的替代解决方案。
在子查询中，列PS2标记 rain started 事件。主查询简单地对此标志求和，同时忽略不下雨的时间。
with ev as (
select measured_at, station_id, ps,
case when ps = 1 and lag(ps,1,0) over (order by measured_at) = 0
then 1 else 0 end ps2
from events)
select measured_at, station_id, ps, ps2,
case when ps = 1 then
sum(ps2) over (order by measured_at) end rf
from ev
;
MEASURED_AT STATION_ID PS PS2 RF
----------- ---------- ---------- ---------- ----------
00:00 32,4 0 0
00:10 32,4 0 0
00:20 32,6 1 1 1
00:30 32,7 1 0 1
00:40 32,9 1 0 1
00:50 33,2 1 0 1
01:00 33,2 0 0
01:10 33,2 0 0
01:20 33,2 0 0
01:30 33,5 1 1 2
01:40 33,6 1 0 2
01:50 33,6 0 0
02:00 33,6 0 0