我有一个road_events
表:
create table road_events (
event_id number(4,0),
road_id number(4,0),
year number(4,0),
from_meas number(10,2),
to_meas number(10,2),
total_road_length number(10,2)
);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (1,1,2020,25,50,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (2,1,2000,25,50,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (3,1,1980,0,25,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (4,1,1960,75,100,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (5,1,1940,1,100,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (6,2,2000,10,30,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (7,2,1975,30,60,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (8,2,1950,50,90,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (9,3,2050,40,90,100);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (10,4,2040,0,200,200);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (11,4,2013,0,199,200);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (12,4,2001,0,200,200);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (13,5,1985,50,70,300);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (14,5,1985,10,50,300);
insert into road_events (event_id, road_id, year, from_meas, to_meas, total_road_length) values (15,5,1965,1,301,300);
commit;
select * from road_events;
EVENT_ID ROAD_ID YEAR FROM_MEAS TO_MEAS TOTAL_ROAD_LENGTH
---------- ---------- ---------- ---------- ---------- -----------------
1 1 2020 25 50 100
2 1 2000 25 50 100
3 1 1980 0 25 100
4 1 1960 75 100 100
5 1 1940 1 100 100
6 2 2000 10 30 100
7 2 1975 30 60 100
8 2 1950 50 90 100
9 3 2050 40 90 100
10 4 2040 0 200 200
11 4 2013 0 199 200
12 4 2001 0 200 200
13 5 1985 50 70 300
14 5 1985 10 50 300
15 5 1965 1 301 300
我想选择代表每条道路上最新作品的事件。
这是一项棘手的操作,因为事件通常只涉及道路的一部分。这意味着我不能简单地选择每条道路的最新事件。我只需要选择不重复的最新 Activity 里程。
可能的逻辑(按顺序):
我不愿意猜测如何解决此问题,因为它最终可能会伤害到其帮助之外(有点像XY Problem)。另一方面,它可以提供对问题本质的洞察力,因此,它就可以了:
event A
。 event A
是>= total_road_length
,那就是我所需要的。该算法到此结束。 event B
),它与event A
的范围不同。 event B
的范围与event A
的范围重叠,则仅获得event B
的不重叠的部分。 = total_road_length
为止。或者,当该路没有更多 Activity 时,停下来。 问题:
我知道这是一个艰巨的任务,但是会怎么做?
这是经典的线性引用问题。如果我可以将线性引用操作作为查询的一部分,那将非常有帮助。
结果将是:
EVENT_ID ROAD_ID YEAR TOTAL_ROAD_LENGTH EVENT_LENGTH
---------- ---------- ---------- ----------------- ------------
1 1 2020 100 25
3 1 1980 100 25
4 1 1960 100 25
5 1 1940 100 25
6 2 2000 100 20
7 2 1975 100 30
8 2 1950 100 30
9 3 2050 100 50
10 4 2040 200 200
13 5 1985 300 20
14 5 1985 300 40
15 5 1965 300 240
相关问题:Select where number range does not overlap
最佳答案
我的主要DBMS是Teradata,但这也可以在Oracle中按原样工作。
WITH all_meas AS
( -- get a distinct list of all from/to points
SELECT road_id, from_meas AS meas
FROM road_events
UNION
SELECT road_id, to_meas
FROM road_events
)
-- select * from all_meas order by 1,2
, all_ranges AS
( -- create from/to ranges
SELECT road_id, meas AS from_meas
,Lead(meas)
Over (PARTITION BY road_id
ORDER BY meas) AS to_meas
FROM all_meas
)
-- SELECT * from all_ranges order by 1,2
, all_event_ranges AS
( -- now match the ranges to the event ranges
SELECT
ar.*
,re.event_id
,re.year
,re.total_road_length
,ar.to_meas - ar.from_meas AS event_length
-- used to filter the latest event as multiple events might cover the same range
,Row_Number()
Over (PARTITION BY ar.road_id, ar.from_meas
ORDER BY year DESC) AS rn
FROM all_ranges ar
JOIN road_events re
ON ar.road_id = re.road_id
AND ar.from_meas < re.to_meas
AND ar.to_meas > re.from_meas
WHERE ar.to_meas IS NOT NULL
)
SELECT event_id, road_id, year, total_road_length, Sum(event_length)
FROM all_event_ranges
WHERE rn = 1 -- latest year only
GROUP BY event_id, road_id, year, total_road_length
ORDER BY road_id, year DESC;
如果您需要返回实际覆盖的
from/to_meas
(如在编辑之前的问题中所示),则可能会更复杂。第一部分是相同的,但是在不进行聚合的情况下,查询可以返回具有相同event_id的相邻行(例如,对于事件3:0-1和1-25):SELECT * FROM all_event_ranges
WHERE rn = 1
ORDER BY road_id, from_meas;
如果要合并相邻的行,还需要两个步骤(使用标准方法,标记组的第一行并计算组号):
WITH all_meas AS
(
SELECT road_id, from_meas AS meas
FROM road_events
UNION
SELECT road_id, to_meas
FROM road_events
)
-- select * from all_meas order by 1,2
, all_ranges AS
(
SELECT road_id, meas AS from_meas
,Lead(meas)
Over (PARTITION BY road_id
ORDER BY meas) AS to_meas
FROM all_meas
)
-- SELECT * from all_ranges order by 1,2
, all_event_ranges AS
(
SELECT
ar.*
,re.event_id
,re.year
,re.total_road_length
,ar.to_meas - ar.from_meas AS event_length
,Row_Number()
Over (PARTITION BY ar.road_id, ar.from_meas
ORDER BY year DESC) AS rn
FROM all_ranges ar
JOIN road_events re
ON ar.road_id = re.road_id
AND ar.from_meas < re.to_meas
AND ar.to_meas > re.from_meas
WHERE ar.to_meas IS NOT NULL
)
-- SELECT * FROM all_event_ranges WHERE rn = 1 ORDER BY road_id, from_meas
, adjacent_events AS
( -- assign 1 to the 1st row of an event
SELECT t.*
,CASE WHEN Lag(event_id)
Over(PARTITION BY road_id
ORDER BY from_meas) = event_id
THEN 0
ELSE 1
END AS flag
FROM all_event_ranges t
WHERE rn = 1
)
-- SELECT * FROM adjacent_events ORDER BY road_id, from_meas
, grouped_events AS
( -- assign a groupnumber to adjacent rows using a Cumulative Sum over 0/1
SELECT t.*
,Sum(flag)
Over (PARTITION BY road_id
ORDER BY from_meas
ROWS Unbounded Preceding) AS grp
FROM adjacent_events t
)
-- SELECT * FROM grouped_events ORDER BY road_id, from_meas
SELECT event_id, road_id, year, Min(from_meas), Max(to_meas), total_road_length, Sum(event_length)
FROM grouped_events
GROUP BY event_id, road_id, grp, year, total_road_length
ORDER BY 2, Min(from_meas);
编辑:
Ups,我刚刚发现一个博客Overlapping ranges with priority与某些简化的Oracle语法完全相同。实际上,我将查询从Teradata中的其他一些简化语法转换为Standard / Oracle SQL :-)
关于sql - 汇总重叠段以测量有效长度,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/52081473/