问题
I have a table that is used to log events. Two types specifically : ON and OFF.
There are sometimes overlapping log entries as there can be 2 simultaneous devices logging. This is not crucial, as the end report should give a [mostly] correct overview of ON -> OFF periods.
Below is a sample, with the 3rd column just for illustration: It does not exist.
ActionTaken ID ID_of_next_OFF
Switched ON 1 3
Switched ON 2 6
Switched OFF 3
Switched ON 4 7
Switched ON 5 8
Switched OFF 6
Switched OFF 7
Switched OFF 8
Switched On 9 10
Switched OFF 10
Switched On 11 12
Switched OFF 12
Given the first two columns, how can I calculate the third?
This does not work:
SELECT actionTaken, Id, LEAD(Id)
OVER (PARTITION BY ActionTaken ORDER BY ID) nextConn
FROM dbo.Events
as it bases the ID_of_Next on the next matching actionTaken value, instead of the next alternate.
回答1:
You are on the right way. All you need is the LEFT JOIN
of the 'Switched ON'
part with the 'Switched OFF'
part on equal row numbers.
with Events as (
select 'Switched ON' as ActionTaken, 1 as ID union all -- 3
select 'Switched ON', 2 union all -- 6
select 'Switched OFF', 3 union all
select 'Switched ON', 4 union all -- 7
select 'Switched ON', 5 union all -- 8
select 'Switched OFF', 6 union all
select 'Switched OFF', 7 union all
select 'Switched OFF', 8 union all
select 'Switched On', 9 union all -- 10
select 'Switched OFF', 10 union all
select 'Switched On', 11 union all -- 12
select 'Switched OFF', 12
), E as (
select
*, row_number() over(partition by ActionTaken order by ID) as rn
from Events
)
select
a.ActionTaken, a.ID, b.ID
from E as a
left join E as b
on a.ActionTaken = 'Switched ON' and
b.ActionTaken = 'Switched OFF' and
a.rn = b.rn
order by a.ID, a.ActionTaken;
Output:
+--------------+----+------+
| ActionTaken | ID | ID |
+--------------+----+------+
| Switched ON | 1 | 3 |
| Switched ON | 2 | 6 |
| Switched OFF | 3 | NULL |
| Switched ON | 4 | 7 |
| Switched ON | 5 | 8 |
| Switched OFF | 6 | NULL |
| Switched OFF | 7 | NULL |
| Switched OFF | 8 | NULL |
| Switched On | 9 | 10 |
| Switched OFF | 10 | NULL |
| Switched On | 11 | 12 |
| Switched OFF | 12 | NULL |
+--------------+----+------+
Test it online with SQL Fiddle.
回答2:
something like this should get you there.
Below I've used 2 CTE's to split the off and on data and then provide a ranking item for first switch on first switch off then I've used a union query to match those up
declare @Events table (
ActionTaken nvarchar(25),
ID int
);
insert @Events
values
--ActionTaken ID ID_of_next_OFF
('Switched ON' , 1), -- 3
('Switched ON' , 2),-- 6
('Switched OFF', 3),
('Switched ON' , 4),-- 7
('Switched ON' , 5),-- 8
('Switched OFF', 6),
('Switched OFF', 7),
('Switched OFF', 8),
('Switched On' , 9),-- 10
('Switched OFF', 10),
('Switched On' , 11),-- 12
('Switched OFF', 12);
with onrank as (
select row_number()over(order by id) ranking, * from @Events where ActionTaken like '%ON')
, offrank as (
select row_number()over(order by id) ranking, * from @Events where ActionTaken like '%OFF')
select o.ActionTaken, o.ID, case when o.ranking=f.ranking then cast(f.id as nvarchar(3)) end as Id_next_off
from onrank o inner join offrank f on o.ranking=f.ranking
union
select ActionTaken, ID, '' from offrank
order by o.ID;
来源:https://stackoverflow.com/questions/56872467/find-next-record-where-status-field-is-different-from-current