Convert datetime stored as char the YYYMMDDHHmmSS format to datetime
Do some string manipulation to get your string to the format YYYYMMDD HH:mm:SS and you can cast/convert to datetime.  

Something like this:

declare @S varchar(50)
set @S = '20120606122012'

select cast(left(@S, 8)+' '+substring(@S, 9, 2)+':'+substring(@S, 11, 2)+':'+substring(@S, 13, 2) as datetime)