Message-ID: <F001.005D2B50.20031010060924@fatcity.com>
Date: Fri, 10 Oct 2003 06:09:24 -0800
To: Multiple recipients of list ORACLE-L <ORACLE-L@fatcity.com>
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From: "Stephane Faroult" <sfaroult@oriolecorp.com>
Subject: RE: RE: RE: Find an unprintable character inside a column....
Organization: Fat City Network Services, San Diego, California
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>Some people have requested this code, so I thought
>you might as well all
>have the chance to pick it to bits... Its a
>function called BAD_ASCII, and
>it hunts out for any ascii characters with an ascii
>value of less than 32 in
>a specified field. (Acknowledgments to my colleague
>Keith Holmes for help
>with this code.)
>
>Use it as follows:
>
>Where a field called DATA in a table TABLE_1 may
>contain an ascci character
>with a value less than 32 (ie a non-printing
>character), the following SQL
>will find the row in question:
>
>select rowid,DATA,dump(DATA) from TABLE_1 
>where BAD_ASCII(DATA) > 0;
>
>You could use the PK of the table instead of rowid,
>of course. You will also
>note that I select the DATA field in both normal
>and ascii 'dump' mode, the
>better to locate where the corruption is located.
>
>peter
>edinburgh
>...................................
>
>Source as follows:
>
>
>Function BAD_ASCII
> (V_Text in char)
> return number
>is
> V_Int  number;
> V_Count number;
>begin
>--
>V_Int	 := 0;
>V_Count := 1;
>while V_Count<=length(rtrim(V_Text)) and V_Int=0
> loop
>  if ascii(substr(V_Text, V_Count, 1))<32 then
>   V_Int := V_Count;
>  end if;
> V_Count := V_Count + 1;
>end loop;
>return V_Int;
>--
>exception
>  when others then
>    return -1;
>end BAD_ASCII;
>/
>

Peter,

   I think that you can make this code 25% faster when the data is clean (which hopefully is the general case) by using 'replace', more efficient than a PL/SQL loop, to check whether you have some rubbish (sort of). It will not tell you where the bad character is, however - which means that then you can loop to look for it.

Here is what I would suggest :

create or replace Function BAD_ASCII (V_Text in char) 
return number 
is 
  V_Int number; 
  V_Count number; 
begin 
  if (replace(V_text, chr(0)||chr(1)||chr(2)||chr(3)||
                      chr(4)||chr(5)||chr(6)||chr(7)||
                      chr(8)||chr(9)||chr(10)||chr(11)||
                      chr(12)||chr(13)||chr(14)||chr(15)||
                      chr(16)||chr(17)||chr(18)||chr(19)||
                      chr(20)||chr(21)||chr(22)||chr(23)||
                      chr(24)||chr(25)||chr(26)||chr(27)||
                      chr(28)||chr(29)||chr(30)||chr(31),
                      '--------------------------------') 
                    = V_text)
  then
    return 0;
  else
    V_Int := 0; 
    V_Count := 1; 
    while V_Count<=length(rtrim(V_Text)) and V_Int=0 
    loop 
      if ascii(substr(V_Text, V_Count, 1))<32 then 
        V_Int := V_Count; 
      end if; 
      V_Count := V_Count + 1; 
    end loop; 
    return V_Int; 
 end if;
-- 
exception 
  when others then 
    return -1; 
end BAD_ASCII; 
/ 

Regards,

Stephane Faroult
Oriole
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Stephane Faroult
  INET: sfaroult@oriolecorp.com

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