Subtract hours from SQL Server 2012 query result

Question

I am running queries on an alarm system signal automation platform database in SQL Server 2012 Management Studio, and I am running into some hiccups.

My queries run just fine, but I am unable to refine my results to the level that I would like.

I am selecting some columns that are formatted as DATETIME, and I simply want to take the value in the column and subtract 4 hours from it (i.e., from GMT to EST) and then output that value into the query results.

All of the documentation I can find regarding DATESUB() or similar commands are showing examples with a specific DATETIME in the syntax, and I don't have anything specific, just 138,000 rows with columns I want to adjust time zones for.

Am I missing something big or will I just need to continue to adjust manually after I being manipulating my query result? Also, in case it makes a difference, I have a read-only access level, and am not interested in altering table data in any way.

Answer 1

Well, for starters, you need to know that you aren't restricted to use functions only on static values, you can use them on columns.

It seems that what you want is simply:

SELECT DATEADD(HOUR,-4,YourColumnWithDateTimes)
FROM dbo.YourTable

Answer 2

Maybe it will be helpful

SELECT DATEPART(HOUR, GETDATE()); 

DATEPART docs from MSDN