Re: NULL values and string

Sergey Karin schrieb:
> Hi, List!
>
> I'm using PG8.1.
>
> Are there any abilities to represent NULL values as string?
>
> I'm doing something like this:
>
> create function func(int4) returns varchar as'
> declare
>     num_value alias for $1;
>     string_value varchar;
> begin
>
>    string_value := \'input value = \' || num_value;
>    return string_value;
>
> end
> 'language 'plpgsql';
>
>
> If I einvoke my function with NULL argument, it return NULL. But I want
> 'input value = NULL'.
> Of course, I can check input value like this:
>
> if(num_value isnull) then
>    string_value := \'input value = NULL\';
> else
>    string_value := \'input_value = \' || num_value;
> end if;
>

You can use COALESCE()


create function func(int4) returns text as $$
declare
     num_value alias for $1;
begin
     return 'input value = ' || COALESCE(num_value,'NULL');
end
$$ language 'plpgsql';


(Id rather use more descriptive name for your function)

Regards
Tino