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;

Answer 2

Cast it to datetime instead:

select CAST(CollectionDate as DATETIME) + CAST(CollectionTime as TIME)
from field

This works on SQL Server 2008 R2.

If for some reason you wanted to make sure the first part doesn't have a time component, first cast the field to date, then back to datetime.

Answer 3

SELECT CONVERT(DATETIME, CONVERT(CHAR(8), date, 112) + ' ' + CONVERT(CHAR(8), time, 108))
  FROM tablename

Answer 4

DECLARE @ADate Date, @ATime Time, @ADateTime Datetime

SELECT @ADate = '2010-02-20', @ATime = '18:53:00.0000000'

SET @ADateTime = CAST   (
    CONVERT(Varchar(10), @ADate, 112) + ' ' +   
    CONVERT(Varchar(8), @ATime) AS DateTime)

SELECT @ADateTime [A nice datetime :)]

This will render you a valid result.

Answer 5

Assuming the underlying data types are date/time/datetime types:

SELECT CONVERT(DATETIME, CONVERT(CHAR(8), CollectionDate, 112) 
  + ' ' + CONVERT(CHAR(8), CollectionTime, 108))
  FROM dbo.whatever;

This will convert CollectionDate and CollectionTime to char sequences, combine them, and then convert them to a datetime.

The parameters to CONVERT are data_type, expression and the optional style (see syntax documentation).

The date and time style value 112 converts to an ISO yyyymmdd format. The style value 108 converts to hh:mi:ss format. Evidently both are 8 characters long which is why the data_type is CHAR(8) for both.

The resulting combined char sequence is in format yyyymmdd hh:mi:ss and then converted to a datetime.

Answer 6

I am using SQL Server 2016 and both myDate and myTime fields are strings. The below tsql statement worked in concatenating them into datetime

select cast((myDate + ' ' + myTime) as datetime) from myTable