Convert varchar data to datetime in SQL server when source data is w/o format

Question

How can I convert VARCHAR data like '20130120161643730' to DATETIME ?

CONVERT(DATETIME, '20130120161643730') does not work.

However, CONVERT (DATETIME, '20130120 16:16:43:730') works. I guess it needs data in correct format.

Is there a valid way that can be used to convert to DATETIME directly from unformatted data ?

My solution is :

DECLARE @Var VARCHAR(100) = '20130120161643730'

SELECT CONCAT(LEFT(@Var,8),' ',SUBSTRING(@var,9,2),':',SUBSTRING(@var,11,2),':',SUBSTRING(@var,13,2),':',RIGHT(@Var,3))

It works fine. However, I'm looking for a compact solution.

Answer 1

You can make it a little more compact by not forcing the dashes, and using STUFF instead of SUBSTRING:

DECLARE @Var VARCHAR(100) = '20130120161643730';

SET @Var = LEFT(@Var, 8) + ' ' 
  + STUFF(STUFF(STUFF(RIGHT(@Var, 9),3,0,':'),6,0,':'),9,0,'.');

SELECT [string] = @Var, [datetime] = CONVERT(DATETIME, @Var);

Results:

string                  datetime
---------------------   -----------------------
20130120 16:16:43.730   2013-01-20 16:16:43.730

Answer 2

DECLARE @var VARCHAR(100) = '20130120161643730'
SELECT convert(datetime,(LEFT(@var,8)+' '+SUBSTRING(@var,9,2)+':'+SUBSTRING(@var,11,2)+':'+SUBSTRING(@var,13,2)+':'+RIGHT(@var,3)))

The only possible way to convert this type of string to date time is to break it and then convert it to DateTime. Also, Concat doesnt work in MS SQL but "+".

Answer 3

Assuming this format is something you work with regularly, something more compact would be to create a UDF (user defined function) that parses the string into a valid datetime.

So something along the lines of:

create function dbo.ParseDate (@var varchar(max)) returns datetime as
begin
  return (convert(datetime,(LEFT(@var,8)+' '+SUBSTRING(@var,9,2)+':'+SUBSTRING(@var,11,2)+':'+SUBSTRING(@var,13,2)+':'+RIGHT(@var,3))))
end

You could then select from that function like this:

select dbo.ParseDate('20130120161643730')

So any code that needed to reference the date would be more compact.