SQL Server连接日期和时间

Question

I have two columns which are "datetime" type in SQL server. However, one columns contains the valid date I need and the other one contains the time(hour, min,..) only.

How can I extract the date from the first column and the time from the last column and concatenate them together into a valid datetime column.

What I have tried:

select 
[Created on],
[Created At],
LEFT([Created On],11),
RIGHT([Created At],8),
LEFT([Created On],11) + RIGHT([Created At],8)
from.. 

However, the output makes sense but I want it to be a valid timestamp type in military format as the first and second columns. How can I do it?

Answer 1

I did some google and this solution below works for me.

select 
[Created on],
[Created At],
CAST(Convert(date, [Created on]) as datetime) + CAST(Convert(time, [Created At]) as datetime),
LEFT([Created On],11) + RIGHT([Created At],8)
from [VERICAL$Purch_ Inv_ Header] 
where [Posting Date] > '2014-02-01

Answer 2

try using this expression:-

select
DATEADD(MILLISECOND,datepart(MILLISECOND,created_at),
DATEADD(SECOND,datepart(SECOND,created_at),
DATEADD(minute,datepart(minute,created_at),
DATEADD(HOUR,datepart(hour,created_at),created_on))))
from ..

It actually finds the time part from the created at column and adds to created on

Answer 3

Grab relevant pieces of date and time from the appropriate column using DATEPART , and piece back together using DATETIMEFROMPARTS (if on SQL Server 2012).

SQLFiddle

Answer 4

Should be able to just add them, +

select 
[Created on],
[Created At],
LEFT([Created On],11),
RIGHT([Created At],8),
[Created On] + [Created At] as whatever

Answer 5

The cleanest way to do it, in my opinion, is to make use of how datetime is implemented by SQL Server: SQL Server implements a datetime value as a pair of signed 32-bit integers.

• The high-order word is the date component. It is the offset in days from the SQL Server's epoch of 1 January 1900.

• The low-order word is the time component. It is the offset in milliseconds from start-of-day (00:00:00.000).

With that knowledge in hand, we can see the implementation thus:

select convert(binary(8),convert(datetime,'March 17, 2014'))

returns

0x0000A2F100000000

and

select convert(binary(8),convert(datetime,'17:55:23'))

returns

0x0000000001275CE4

So, to meld the date component of one datetime value with the time component of another:

convert(datetime,
    substring(convert(binary(8),date_only_column),1,4)
  + substring(convert(binary(8),time_only_column),5,4)
  )

Easy!

And to format as an ISO 8601 string:

convert(varchar(32),
  convert(datetime,
      substring(convert(binary(8),date_only_column),1,4)
    + substring(convert(binary(8),time_only_column),5,4)
    ) ,
    120 -- or 121 if your want milliseconds.
  )