DSXchange

Search here for the phrase "double convert", you can use two embedded Convert() functions to remove characters by providing a list to keep. For example, to keep all of the numerics:
The inner convert removes all numbers from your string, leaving just the non-numeric characters. The outer convert then removes the list of unwanted characters from your field.

Do the opposite by providing a list of the alphabetic characters you'd like to keep.

To get only alphabetic values use this Convert(Convert('ABCD..Z','',Upcase(Col)),'',Col) and to get numeric values only replace the alphabets with numbers..