Select left

I am trying to select data from the left of a delimiter.  I have a
part number like ABCD123-TOP all of the part numbers are like this.  I
want to select the data to the left of the -.  The kicker is the data
to the left of the - is not of a standard length.  It might be 5
characters or 20 but whatever it is I want it.  Any ideas?