T-SQL How to update hour in a SmallDateTime column? - tsql

Question

let's say that I have a SmallDateTime column in my table. How to update hours in each row in T-SQL ?

Answer 1

Get the target value's hour part.
Find the difference between the hour you want and the found hour.
Add the difference of hours to the target value.
The script:
UPDATE atable
SET datetimevalue = DATEADD(hour, #hour - DATEPART(hour, datetimevalue),
datetimevalue)
WHERE ...

Answer 2

UPDATE YourTable SET YourDateColumn = DateAdd(hh, 1, YourDateColumn)
will add 1 hour to the time value in YourDateColumn in every single row.
See this page for more info.

Answer 3

UPDATE YourTableName
SET YourSmallDateTimeColumn = DATEADD(HH, 1, YourSmallDateTimeColumn)
Will add any number of hours to your column. So if you get rid of the time component first:
SELECT CAST(CONVERT(char(8), YourSmallDateTimeColumn, 112) AS smalldatetime)
and add hour component to it later it should work.
From here
To add or subtract hours to a datetime
or smalldatetime value, you will use
the DATEADD date function. The
DATEADD date function returns a new
datetime value based on adding an
interval to the specified date. The
syntax of the DATEADD date function is
as follows:
DATEADD ( datepart , number, date )
datepart is the parameter that
specifies on which part of the date to
return a new value. For hours, you
can use either HOUR or HH. number is
the value used to increment datepart.
date is an expression that returns a
datetime or smalldatetime value, or a
character string in a date format.
Here's an example on how to use the
DATEADD date function to increase or
decrease a datetime value by a certain
number of hours:
SELECT DATEADD(HOUR, -12, GETDATE())AS [TwelveHoursAgo]
SELECT DATEADD(HH, 6, GETDATE()) AS [SixHoursLater]