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

Concat date of one column with a time of another column in MySQL.

SELECT CONVERT(concat(CONVERT('dateColumn',DATE),' ',CONVERT('timeColumn', TIME)), DATETIME) AS 'formattedDate' FROM dbs.tableName;

Answer 2

The simple solution

SELECT CAST(CollectionDate as DATETIME) + CAST(CollectionTime as DATETIME)
FROM field

Answer 3

Solution (1): datetime arithmetic

Given @myDate, which can be anything that can be cast as a DATE, and @myTime, which can be anything that can be cast as a TIME, starting SQL Server 2014+ this works fine and does not involve string manipulation:

CAST(CAST(@myDate as DATE) AS DATETIME) + CAST(CAST(@myTime as TIME) as DATETIME)

You can verify with:

SELECT  GETDATE(), 
        CAST(CAST(GETDATE() as DATE) AS DATETIME) + CAST(CAST(GETDATE() as TIME) as DATETIME)

Solution (2): string manipulation

SELECT  GETDATE(), 
        CONVERT(DATETIME, CONVERT(CHAR(8), GETDATE(), 112) + ' ' + CONVERT(CHAR(8), GETDATE(), 108))

However, solution (1) is not only 2-3x faster than solution (2), it also preserves the microsecond part.

See SQL Fiddle for the solution (1) using date arithmetic vs solution (2) involving string manipulation

Answer 4

dealing with dates, dateadd must be used for precision

declare @a DATE = getdate()
declare @b time(7) = getdate()
select @b, @A, GETDATE(), DATEADD(day, DATEDIFF(day, 0, @a), cast(@b as datetime2(0)))

Answer 5

An easier solution (tested on SQL Server 2014 SP1 CU6)

Code:

DECLARE @Date date = SYSDATETIME();

DECLARE @Time time(0) = SYSDATETIME();

SELECT CAST(CONCAT(@Date, ' ', @Time) AS datetime2(0));

This would also work given a table with a specific date and a specific time field. I use this method frequently given that we have vendor data that uses date and time in two separate fields.

Answer 6

drop table test

create table test(
    CollectionDate date NULL,
    CollectionTime  [time](0) NULL,
    CollectionDateTime as (isnull(convert(datetime,CollectionDate)+convert(datetime,CollectionTime),CollectionDate))
-- if CollectionDate is datetime no need to convert it above
)

insert test (CollectionDate, CollectionTime)
values ('2013-12-10', '22:51:19.227'),
       ('2013-12-10', null),
       (null, '22:51:19.227')

select * from test

CollectionDate  CollectionTime  CollectionDateTime
2013-12-10      22:51:19        2013-12-10 22:51:19.000
2013-12-10      NULL            2013-12-10 00:00:00.000
NULL            22:51:19        NULL