How to get a 'when others' exception raised.

Question

the 'when others' exception is raised usualy after a error occurs, but when does this actually occur? could some1 give an example??
usually some error occurs and then a inbuilt exception is raised. but 'others' exception never seems to take place?

Answer 1

The OTHERS handler takes control when the exception is not handled by any previous handlers.
Here, we'll try to divide by zero. The no_data_found handler does not handle this error so control passes to the OTHERS section:
sql>declare
  2    n  number;
  3  begin
  4    n := 1/0;
  5  exception
  6    when no_data_found then
  7      dbms_output.put_line( 'no data found exception' );     
  8    when others then
  9      dbms_output.put_line( 'when others exception' );
10  end;
11  /
when others exception
PL/SQL procedure successfully completed.Now, we'll try an operation which will raise the no_data_found exception. Here the ndf handler does handle the error and control never passes to the OTHERS section:
sql>declare
  2    n  number;
  3  begin
  4    select 0
  5      into n
  6      from dual
  7     where dummy is null;
  8  exception
  9    when no_data_found then
10      dbms_output.put_line( 'no data found exception' );
11    when others then
12      dbms_output.put_line( 'when others exception' );
13  end;
14  /
no data found exception
PL/SQL procedure successfully completed.