Combining (concatenating) date and time into a datetime

Question

Using SQL Server 2008, this query works great:

select CAST(CollectionDate as DATE), CAST(CollectionTime as TIME)
from field

Gives me two co

Answer 1

This works in SQL 2008 and 2012 to produce datetime2:

declare @date date = current_timestamp;
declare @time time = current_timestamp;

select 
@date as date
,@time as time
,cast(@date as datetime) + cast(@time as datetime) as datetime
,cast(@time as datetime2) as timeAsDateTime2
,dateadd(dayofyear,datepart(dayofyear,@date) - 1,dateadd(year,datepart(year,@date) - 1900,cast(@time as datetime2))) as datetime2;