Deleting Decimals From Text Fields

Could someone please advise me on how I should go about doing this?

I have a number of cells (over 250,000 rows of data) with references like ABC0001 and ABC0001.01. The reference ending .01 refers to an amendment of a record and yet I want to link that reference to the original (ABC0001). I.e. I need to have a separate column which will lookup data based upon the original field.

I therefore need to devise a formula that deletes the last 2 characters (and the decimal) if a decimal is found in a text field.

Can anyone help please? I'm really stuck....

=left(a1,(find(".",a1,1)-1))

Thanks! That does work, but for those with original references (no decimals) it returns #VALUE!

I could go and delete the formula from those that have this response, but might there be a better formula?

=if(iserror(find(".",a1,1)),a1,left(a1,(find(".",a1,1)-1)))