How can I condition the time column?

There is a column representing 24 hours. Data comes in every 15 minutes. For example, at 10:15, the value is entered in the DateTime column of the 10H column. But… The client wants to set the standard for the day at 6:30 a.m. and set it to 6:30 the next day. If you look at the column below, should sum the value from column 6h.. Is there any way?

DateTime             0H  1H   ..6H....7H...8H..9H..10H..~23H
2020 11 10 00:00:00  979 958 
2020 11 10 00:15:00  987 954 
2020 11 10 00:30:00  987 958 
2020 11 10 00:45:00  960 956 
2020 11 11 00:00:00    0 0 
2020 11 11 00:15:00    0 0 
2020 11 11 00:30:00    0 0 
2020 11 11 00:45:00    0 0 
2020 11 12 00:00:00  995 995 
2020 11 12 00:15:00  991 993 
2020 11 12 00:30:00 1000 993 
2020 11 12 00:45:00  993 996 

I want value
2020-11-15 06:30 ~ 2020-11-16 06:30 values sum

Answer

Consider breaking hour blocks into separate SELECT segments that add corresponding hour columns. Then, bind all parts together by UNION ALL. Finally, aggregate all hour blocks for final SUM.

Below sums all values between 2020-11-15 06:30 - 2020-11-16 06:30 (not including upper limit). Be sure to fill in the abbreviated ... for needed columns:

SELECT SUM(sub.HoursTotal) AS DayTotal
FROM
   (
    -- PARTIAL HOUR - 6:30 AM - 6:45 AM
    SELECT [6h] AS HoursTotal
    FROM myTable
    WHERE logdatetime BETWEEN '2020 11-15 00:30:00' AND  
                              '2020 11-15 00:45:00'

    UNION ALL

    -- FULL HOURS - 7:00 AM - 23:00 PM
    SELECT [7h] + [8h] + ... + [23h] AS HoursTotal
    FROM myTable
    WHERE logdatetime BETWEEN '2020 11-15 00:00:00' AND  
                              '2020 11-15 00:45:00'

    UNION ALL

    -- FULL HOURS - 12:00 AM - 5:00 AM
    SELECT [0h] + [1h] + ... + [5h] AS HoursTotal
    FROM myTable
    WHERE logdatetime BETWEEN '2020 11-16 00:00:00' AND  
                              '2020 11-16 00:45:00'
 
    UNION ALL

    -- PARTIAL HOUR - 6:00 AM - 6:15 AM
    SELECT [6h] AS HoursTotal
    FROM myTable
    WHERE logdatetime BETWEEN '2020 11-16 00:00:00' AND  
                              '2020 11-16 00:15:00'
  ) sub

Of course, ideally your table maintains a normalized structure of long format with two columns for datetime and value. Then, querying is much easier:

logDateTimewithHour   Value
2020 11-15 00:00:00     ###
2020 11-15 00:15:00     ###
2020 11-15 00:30:00     ###
2020 11-15 00:45:00     ###
2020 11-15 01:00:00     ###
2020 11-15 01:15:00     ###
2020 11-15 01:30:00     ###
2020 11-15 01:45:00     ###
...                     ...
2020 11-16 22:00:00     ###
2020 11-16 22:15:00     ###
2020 11-16 22:30:00     ###
2020 11-16 22:45:00     ###
2020 11-16 23:00:00     ###
2020 11-16 23:15:00     ###
2020 11-16 23:30:00     ###
2020 11-16 23:45:00     ###

SELECT SUM(Value) AS DayTotal
FROM myLongTable
WHERE logDateTimewithHour BETWEEN '2020 11-15 06:30:00'
                              AND '2020 11-16 06:15:00'