Обсуждение: Determine if a string is digit

Hello list,

That's my question, I can't figure out a way to know if a given string
is digit, soemthing like this:

ISDIGIT("ARWA") = False
ISDIGIT("5334")    = True

If anyone know a way to get that done, I'll appreciate the help.

--
Josué Maldonado.

Josué Maldonado <josue@lamundial.hn> writes:

> Hello list,
>
> That's my question, I can't figure out a way to know if a given string is
> digit, soemthing like this:
>
>
> ISDIGIT("ARWA") = False
> ISDIGIT("5334")    = True
>
> If anyone know a way to get that done, I'll appreciate the help.

create function isdigit(text) returns boolean as '
select $1 ~ ''^(-)?[0-9]+$'' as result
' language sql;

masm=# select isdigit('ARWA');
 isdigit
---------
 f
(1 row)

masm=# select isdigit('5334');
 isdigit
---------
 t
(1 row)

Regards,
Manuel.

Thanks Manuel,

It works nice!

Manuel Sugawara wrote:

> Josué Maldonado <josue@lamundial.hn> writes:
>
>
>>Hello list,
>>
>>That's my question, I can't figure out a way to know if a given string is
>>digit, soemthing like this:
>>
>>
>>ISDIGIT("ARWA") = False
>>ISDIGIT("5334")    = True
>>
>>If anyone know a way to get that done, I'll appreciate the help.
>
>
> create function isdigit(text) returns boolean as '
> select $1 ~ ''^(-)?[0-9]+$'' as result
> ' language sql;
>
> masm=# select isdigit('ARWA');
>  isdigit
> ---------
>  f
> (1 row)
>
> masm=# select isdigit('5334');
>  isdigit
> ---------
>  t
> (1 row)
>
> Regards,
> Manuel.
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match
>


--
Josué Maldonado.

Josué Maldonado wrote:

> Hello list,
>
> That's my question, I can't figure out a way to know if a given string
> is digit, soemthing like this:
>
> ISDIGIT("ARWA") = False
> ISDIGIT("5334")    = True
>
> If anyone know a way to get that done, I'll appreciate the help.
>
Check out the postgresql cookbook
(http://www.brasileiro.net/postgres/cookbook/). I've added the following
function:

CREATE OR REPLACE FUNCTION isdigit(text) RETURNS boolean as '

-- by Ron St.Pierre (rstpierre@syscor.com)
-- licensed under the GPL
--
-- determines whether or not a value is numeric
--
-- required fields:   string or number, single quoted
-- returns:           true - if input is numeric, false otherwise
--
       DECLARE
               inputText ALIAS FOR $1;
               tempChar text;
               isNumeric boolean;
                      BEGIN
               isNumeric = true;
               FOR i IN 1..length(inputText) LOOP
tempChar := substr(inputText, i, 1);
                   IF tempChar ~ ''[0-9]'' THEN
                       -- do nothing
                   ELSE
                       return FALSE;
                   END IF;
               END LOOP;
                              return isNumeric;
       END;
' LANGUAGE 'plpgsql';

You need plpgsql installed for your database. Also you can use unquoted
numbers or single quoted text or numbers, double quoted values do not work.
eg
imperial=# select isdigit('234');
isdigit
---------
t
(1 row)

imperial=# select isdigit('asdf');
isdigit
---------
f
(1 row)

Ron