plsql/cursors handle exception and return back to the execution flow

Question

I am trying to execute a cursor and want it to complete the loop even if there is some exception.

What I trying to do is "catch" all the exception and probably log something or do nothing and then return back to the flow . Here is how the code looks like:

 FOR line IN my_cursor
 LOOP
 begin
        
    if<condition> then
      GOTO pass; 
    else     
     <<do_something>>
     exception
       when others then
        sys.dbms_output.put_line('say something');       
    end if;  

    <<pass>> null;
 end
 END LOOP;

The script doesn't compile.

There is probably some syntax error with the exception, but I am also not aware of semantics very well. Like I am not sure if you can return back to execution flow after handling an exception.

p.s: The DB is 10g and there is not CONTINUE in it. Hence using GOTO.

Solution 1

Put the code that you want to execute within the loop in it's own block and then you can use that blocks exception section to handle any problems during the loop iteration.

Once the exception for that iteration is handled, the next loop iteration will start

e.g.:

for line in my_cursor
loop
   begin    
      <<do_something>>
   exception
      <<do_exception_processing>>        
   end;
end loop;

To illustrate this further, in the example below, I have declared a local variable of type exception. I am looping through numbers 1 to 10, during the second loop iteration, the if statement is true and processing passes to the exception handler. Once the exception is handled, the next iteration of the loop begins.

begin

   for i in 1 .. 10 
   loop

      declare

         my_exception exception;

      begin

         if i = 2
         then

            -- if you need to do some processing then you would enter it
            -- here and then when you want to enter the exception section 
            -- you would add the line below 

            raise my_exception;

         end if;

      exception
         when my_exception then
            dbms_output.put_line('in exception section');

      end;

   end loop;

end;

Solution 2

FOR line IN my_cursor  
LOOP
  if not some_condition then
    begin
      do_something;
    exception     
      when others then log_my_error(); -- this should be something that uses
                                       -- an autonomous transaction
    end;
  end if;
END LOOP; 

Comments

[codeObserver]

Thnx Ian. I tried that and updated in the question. Still have issues.Btw is there a need for "begin" and "end" in the LOOP ?

[Ian Carpenter]

Yes, in order to use the exception section the begin .. end sections are required

[codeObserver]

thnx. I added begin and end , there are still more errors in the structure. Also note that there is also an else statement which initially I thought is irrelevant, but I dont know :). I updated in the questions. Thanks again !

[Luc M]

<<do_something>> has to be executed only when condition is false. Not always...

[codeObserver]

@LucM . was that a question? Yes ..I want everything in else [including the exception block] to be executed only when the <<condition>> is false.

[Luc M]

@codeObserver It was what I meant. Ian Carpenter has edited his answer. With his old answer, <<do_something>> was always executed.

[Shannon Severance]

An exception block can not sit inside anything except a begin block. Your question now has it inside the else part of an if statement. If you want the exception there, you will need a begin after the else then exception at the point you are done with everthing in theelse and finally an end; to close the begin before the end if.