Solve: instr/substr

Question

Please help solve this question i am stuck on
We have the following value that we can use:
Numeric: 0-34 and 80-100 only
or Non Numberic X S U D- D D+
Have to use INSTR and SUBSTR functions to test that the value is a valid
(for now only trying to create a function which can later be put into a procedure.)
SELECT TO_NUMBER('12 ') //e.g HERE 12 and a space for the values as above
FROM DUAL
the where clause looks at all three spaces to make sure values are correct (given number or non-numberic values only)
(Hence if the number is true then number comes back (meaning true)
or it says NO rows)
If value is non numeric, test it to allow non numberic also.
I am completely unsure about it but tried this
SELECT TO_NUMBER('34 ')
FROM DUAL
WHERE INSTR('0123456789',1,1)<=9 (looking at first number ?)
AND
INSTR('0123456789',2,2)<=9
AND
INSTR('0123456789',3,3)=0;
Something like this has to be done.....subst (instr, x,x,) i think mite help.

Answer 1

Why not use regular expressions? The below thread gives you an example and instructions on how to use.
alphanumeric validation