plsql 异常

http://chenhua-1984.iteye.com/blog/990970

http://chenhua-1984.iteye.com/blog/996018

 

begin

  begin
  while(true)
  loop
    select seq_user_number.nextval into result from dual;
    select user_number into user_number from  user_number where user_number=result;
    end loop;
 exception
     when no_data_found then 
        dbms_output.put_line(result);  
 end;
    return result;

end;