PL-SQL Solve: Using INSTR and SUBSTR

Question

I am trying to work on this and cannot get a solution. Please help
You have to use INSTR and SUBSTR to solve
Question:
You have the following acceptable value
Numberic: 0-34
80-100
or Non Numberic X S U D- D D+
Im have to use INSTR and SUBSTR functions to test that the value is a valid (as above) number before TO_NUMBER is called:
SELECT TO_NUMBER('?? ') //HERE ?? and a space (for 100 etc) is for the values as above
FROM DUAL
WHERE ....INSTR(......)<=;
(Hence if the number is true then number comes back or it says no rows)
and also id non numberic it should also be tested.
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;
Please help

Answer 1

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.