我在现有表中获取了包含事件 (a) 和非事件 (i) 等事件的数据。它类似于记录组件是否处于事件状态。由于接口(interface)较旧,因此没有正确的组件对。
Hier 是简短的示例数据库
"id" "component_number" "timestamp" "status"
"1" "1" "2020-05-10 16:30:00" "A"
"2" "1" "2020-05-18 16:34:05" "A"
"3" "1" "2020-05-19 16:36:01" "I"
"4" "1" "2020-05-19 16:36:52" "A"
"5" "1" "2020-05-19 16:38:57" "I"
"6" "2" "2020-05-11 17:04:50" "A"
"7" "2" "2020-05-15 10:00:00" "A"
"8" "2" "2020-05-16 11:25:16" "I"
例如,发动机编号 1 于 2020-05-10 16:30:00 启动(事件),并于 2020-05-19 16:36:01 停止(非事件)。但我在 2020-05-18 16:34:05 获得了一个活跃的额外条目。
当发动机运转时,我必须找到正确的对。这将是在示例中: 2020-05-10 16:30:00 和 2020-05-19 16:36:01。该列表不仅包括一个引擎,还可以有更多引擎。
我正在寻找一个查询字符串来获取正确的对(结果 1)或一个字符串来获取所需的事件(结果 2)。不知道还有什么更容易的呢?
结果 1:
"component_number" "start" "end"
"1" "2020-05-10 16:30:00" "2020-05-19 16:36:01"
"1" "2020-05-19 16:36:52" "2020-05-19 16:38:57"
"2" "2020-05-11 17:04:50" "2020-05-16 11:25:16"
结果 2:
"id" "component_number" "timestamp" "status"
"1" "1" "2020-05-10 16:30:00" "A"
"3" "1" "2020-05-19 16:36:01" "I"
"4" "1" "2020-05-19 16:36:52" "A"
"5" "1" "2020-05-19 16:38:57" "I"
"6" "2" "2020-05-11 17:04:50" "A"
"8" "2" "2020-05-16 11:25:16" "I"
我尝试了子查询和连接,但没有成功。有人有想法或提示如何处理它吗?
最佳答案
这是一个间隙和孤岛问题。我建议使用 lag()
和窗口 sum()
来定义组。基本上,每个 'A'
都会启动一个新组,前面有一个 'I'
。
这将为您提供第一个结果集:
select
component_number,
min(timestamp) start_timestamp,
max(timestamp) end_timestamp
from (
select
t.*,
sum(case when status = 'A' and lag_status = 'I' then 1 else 0 end)
over(partition by component_number order by timestamp) grp
from (
select
t.*,
lag(status)
over(partition by component_number order by timestamp) lag_status
from mytable t
) t
) t
group by component_number, grp
第二个结果集需要更少的嵌套:
select id, component_number, timestamp, status
from (
select
t.*,
lag(status)
over(partition by component_number order by timestamp) lag_status
from mytable t
) t
where status = 'I' or lag_status is null or lag_status = 'I'
<强> Demo on DB Fiddle (MariaDB 10.3):
component_number | start_timestamp | end_timestamp ---------------: | :------------------ | :------------------ 1 | 2020-05-10 16:30:00 | 2020-05-19 16:36:01 1 | 2020-05-19 16:36:52 | 2020-05-19 16:38:57 2 | 2020-05-11 17:04:50 | 2020-05-16 11:25:16
id | component_number | timestamp | status -: | ---------------: | :------------------ | :----- 1 | 1 | 2020-05-10 16:30:00 | A 3 | 1 | 2020-05-19 16:36:01 | I 4 | 1 | 2020-05-19 16:36:52 | A 5 | 1 | 2020-05-19 16:38:57 | I 6 | 2 | 2020-05-11 17:04:50 | A 8 | 2 | 2020-05-16 11:25:16 | I
关于mysql - SQL 查询查找正确运行的引擎对,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61894732/