Converting a datestring to datetime (yyyymmddhhmmss)

This uses STUFF to format a datestring correctly.

declare @datestring varchar(20) = '20170504103253'
-- Add colons and space to format datetime
SET @datestring = STUFF(STUFF(STUFF(@datestring,13,0,':'),11,0,':'),9,0,' ')
select @datestring
-- Convert ....
select convert(datetime,@datestring)

2017-05-04 10:32:53

2017-05-04 10:32:53.000