SQL Server: query to get the data between two values from same columns and calculate time difference - sql

Question

I have a requirement to get the number of hours between two values, say 20 and 25 or above (this will be user input values and not fixed). Below is the table with sample data.
Consider in the table on 01-09-2016 08:40 value_ID is 25 and it reaches back to 20 on 02-09-2016 13:20, I need to consider the number of hours between these two range ie 12 hours and 40 min it is .. Similarly 04-09-2016 13:20 it reached 26.3 (which is above 25 ) and '06-09-2016 16:20' reached 19.3 (below 20) and number of hours is 45 hours. I tried creating a function, however it's not working..
CODE TO CREATE TABLE:
CREATE TABLE [dbo].[NumOfHrs](
[ID] [float] NULL,
[Date] [datetime] NULL,
[Value_ID] [float] NULL
) ON [PRIMARY]
CODE to insert data :
INSERT INTO [dbo].[NumOfHrs]
([ID]
,[Date]
,[Value_ID])
VALUES
(112233,'8-31-2016 08:20:00',19.2),
(112233,'9-01-2016 08:30:00',24),
(112233,'9-01-2016 08:40:00',25),
(112233,'9-01-2016 09:20:00',26),
(112233,'9-02-2016 10:20:00',27),
(112233,'9-02-2016 10:20:00',24),
(112233,'9-02-2016 10:20:00',23),
(112233,'9-02-2016 11:20:00',22),
(112233,'9-02-2016 12:20:00',21),
(112233,'9-02-2016 13:20:00',20),
(112233,'9-03-2016 13:20:00',19.8),
(112233,'9-04-2016 13:20:00',21),
(112233,'9-04-2016 14:20:00',24),
(112233,'9-04-2016 16:20:00',24.6),
(112233,'9-04-2016 19:20:00',26.3),
(112233,'9-04-2016 23:20:00',27),
(112233,'9-05-2016 00:20:00',22),
(112233,'9-06-2016 16:20:00',19.3),
(112233,'9-07-2016 00:20:00',22),
(112233,'9-08-2016 00:20:00',21),
(112233,'9-09-2016 00:20:00',23),
(445566,'9-10-2016 00:20:00',24),
(445566,'9-11-2016 00:20:00',25),
(445566,'9-12-2016 00:20:00',26),
(445566,'9-13-2016 00:20:00',24),
(445566,'9-14-2016 00:20:00',23),
(445566,'9-15-2016 00:20:00',24),
(445566,'9-16-2016 00:20:00',21),
(445566,'9-17-2016 00:20:00',20),
(445566,'9-18-2016 00:20:00',18.5),
(445566,'9-19-2016 00:20:00',17)
image of the table:

Answer 1

Well, I couldn't think of anything simpler. Here's my try to solve the problem:
;with NumOfHrs_rn as (
select id, [Date], Value_ID,
row_number() over (partition by id order by [date]) AS rn
from [dbo].[NumOfHrs]
), NumOfHrs_lag as (
select t1.id, t1.[date],
t2.Value_ID as prev_value,
t1.Value_ID as curr_value
from NumOfHrs_rn as t1
-- get previous value (lag)
join NumOfHrs_rn as t2 on t1.id = t2.id and t1.rn = t2.rn + 1
), NumOfHrs_flag as (
select id, [Date], prev_value, curr_value,
case
when curr_value >= 25 and prev_value < 25 then 'start'
when curr_value <= 20 and prev_value > 20 then 'stop'
else 'ignore'
end as flag
from NumOfHrs_lag
), NumOfHrs_grp as (
select id, [Date], curr_value, flag,
row_number() over (partition by id order by [Date]) -
case flag
when 'start' then 0
when 'stop' then 1
end as grp
from NumOfHrs_flag
where flag in ('start', 'stop')
)
select min([Date]) AS 'start', max([Date]) as 'stop'
from NumOfHrs_grp
group by id, grp
order by min([Date])
Output:
start stop
------------------------------------------------
2016-09-01 08:40:00.000 2016-09-02 13:20:00.000
2016-09-04 19:20:00.000 2016-09-06 16:20:00.000
2016-09-11 00:20:00.000 2016-09-17 00:20:00.000
You can manipulate the above query in order to get the time difference expressed in hours/minutes/seconds format.
Demo here