Add two datetime columns and divide result by 2 in SQL Server - sql

Question

If actual start date != ‘’ and complete date != '' calculate the mid trim date = (actual start date + complete date)/2
My table
CREATE TABLE [dbo].[AR_Placebook]
(
[Region] nvarchar(255) NULL,
[Network Area Description] [nvarchar](255) NULL,
[Substation] [nvarchar](255) NULL,
[Circuit] [nvarchar](255) NULL,
[Original (O) or Added Circuit (A)] [nvarchar](255) NULL,
[OC] [nvarchar](255) NULL,
[Line Miles] [float] NULL,
[Line Miles Complete] [float] NULL,
[Percent Complete] [float] NULL,
[Contractor] [float] NULL,
[Final Circuit Performance Audit] [nvarchar](255) NULL,
[Should Be Billed] [float] NULL,
[Invoiced to Date] [float] NULL,
[Gap in Billing Difference] [float] NULL,
[VCKT Number] [nvarchar](255) NULL,
[Bid Cost ] [float] NULL,
[Bid Cost per Line Mile] [float] NULL,
[Predictive Dialer Start Date] [nvarchar](255) NULL,
[ESTIMATED TRIM QUARTER] [nvarchar](255) NULL,
[Actual Start Date] [datetime] NULL,
[Complete Date] [datetime] NULL,
[MidTrimDate] [datetime] NULL
)
I have tried this
DECLARE #StartTime DATETIME
,#EndTime DATETIME
DECLARE #TotalWorkingHours varchar(50)
Declare #HalfDayCalculate varchar(50)
Declare #DivdeWorkingHours int
set #DivdeWorkingHours=2
SELECT #TotalWorkingHours = CONVERT(VARCHAR(8), DATEADD(SECOND,DATEDIFF(SECOND,#StartTime, #EndTime),0), 108)
from AR_Placebook
where #StartTime=[Actual Start Date] and
#EndTime =[Complete Date] and
[Actual Start Date]!='' and
[Complete Date]!=''
set #HalfDayCalculate = convert(TIME(0), dateadd(second, datediff(second, 0, #TotalWorkingHours) / #DivdeWorkingHours, 0),108)
select #HalfDayCalculate as MidTrimDate

Answer 1

You can go with different approach - calculate the date difference between the two dates using DATEDIFF (https://learn.microsoft.com/en-us/sql/t-sql/functions/datediff-transact-sql?view=sql-server-ver15), divide the result of the DATEDIFF by 2 and subtract this value from the complete date.

Answer 2

Please find below the answer as per your requirement.
SELECT [start date],DATEADD(DAY,day_difference,[start date]) AS [mid_date],[complete date],day_difference
FROM
(
SELECT '2020-03-01' AS[start date], '2020-03-20' AS[complete date],DATEDIFF(DAY,'2020-03-01' ,'2020-03-20')/2 as day_difference
)A
Also, find below snap.
enter image description here

Answer 3

If actual start date != ‘’ and complete date != '' calculate the mid trim date = (actual start date + complete date)/2
I think you are looking for. For the middle day:
select dateadd(day,
datediff(day, start_date, complete_date) / 2,
start_date
)
If there is a time component, use a smaller time unit:
select dateadd(second,
datediff(second, start_date, complete_date) / 2,
start_date
)