checking for non-numeric and numeric values in substr

Hi All,

I need your assistance. I have a simple select statement below but I am struggling with non-numeric and numeric values. I would like to check if characters 2 to 7 of 'VHT56789TYHBG' are numeric and if characters 2 to 7 of 'VHT56789TYHBG' are non-numeric and to remove 1st and last 2 characters of 'VHT56789TYHBG'.

Thanks in advance.




select
CASE
WHEN substr('VHT56789TYHBG',2,7) –how to check for numeric
THEN substr('VHT56789TYHBG',,8,2)
WHEN substr('VHT56789TYHBG',,2,7) –how to check for non-numeric
THEN substr('VHT56789TYHBG',)—then remove 1st and last 2 characters
ELSE
'VHT56789TYHBG',
END
from dual