SubString in sql for File Extension

SELECT RIGHT('myFile3333333333333333.txt',
               CHARINDEX('.', REVERSE('myFile.txt'))-1) AS 'File Extension'


case lower(RIGHT(dc.UploadFile,
               CHARINDEX('.', REVERSE('.zip'))-1)) when 'xls' then 'ver11xls_icon'  when 'zip' then 'ver11zip_icon' else 'none' end