check if “it's a number” function in Oracle

Question

I\'m trying to check if a value from a column in an oracle (10g) query is a number in order to compare it. Something like:

select case when ( is_number(myTab         


        

Answer 1

Note that regexp or function approaches are several times slower than plain sql condition.

So some heuristic workarounds with limited applicability make sence for huge scans.

There is a solution for cases when you know for sure that non-numeric values would contain some alphabetic letters:

select case when upper(dummy)=lower(dummy) then '~numeric' else '~alpabetic' end from dual

And if you know some letter would be always present in non-numeric cases:

select case when instr(dummy, 'X')>0 then '~alpabetic' else '~numeric' end from dual

When numeric cases would always contain zero:

select case when instr(dummy, '0')=0 then '~alpabetic' else '~numeric' end from dual

Answer 2

@JustinCave - The "when value_error" replacement for "when others" is a nice refinement to your approach above. This slight additional tweak, while conceptually the same, removes the requirement for the definition of and consequent memory allocation to your l_num variable:

function validNumber(vSomeValue IN varchar2)
     return varchar2 DETERMINISTIC PARALLEL_ENABLE
     is
begin
  return case when abs(vSomeValue) >= 0 then 'T' end;
exception
  when value_error then
    return 'F';
end;

Just a note also to anyone preferring to emulate Oracle number format logic using the "riskier" REGEXP approach, please don't forget to consider NLS_NUMERIC_CHARACTERS and NLS_TERRITORY.

Answer 3

I'm against using when others so I would use (returning an "boolean integer" due to SQL not suppporting booleans)

create or replace function is_number(param in varchar2) return integer
 is
   ret number;
 begin
    ret := to_number(param);
    return 1; --true
 exception
    when invalid_number then return 0;
 end;

In the SQL call you would use something like

select case when ( is_number(myTable.id)=1 and (myTable.id >'0') ) 
            then 'Is a number greater than 0' 
            else 'it is not a number or is not greater than 0' 
       end as valuetype  
  from table myTable

Answer 4

This is a potential duplicate of Finding rows that don't contain numeric data in Oracle. Also see: How can I determine if a string is numeric in SQL?.

Here's a solution based on Michael Durrant's that works for integers.

SELECT foo
FROM bar
WHERE DECODE(TRIM(TRANSLATE(your_number,'0123456789',' ')), NULL, 'number','contains char') = 'number'

Adrian Carneiro posted a solution that works for decimals and others. However, as Justin Cave pointed out, this will incorrectly classify strings like '123.45.23.234' or '131+234'.

SELECT foo
FROM bar
WHERE DECODE(TRIM(TRANSLATE(your_number,'+-.0123456789',' ')), NULL, 'number','contains char') = 'number'

If you need a solution without PL/SQL or REGEXP_LIKE, this may help.