Simple LOOP

The simplest way of iterating the execution of a statement in PL/SQL is achieved through the LOOP statement. And the simplest form of LOOP is this:

loop
  (...)
end loop;

We normally want to stop a loop execution, and there are two polite ways of terminating a simple loop: through the EXIT and the EXIT WHEN statements.

Here is an example of a LOOP in an anonymous block terminated by EXIT:

declare
  l_value integer := 3;
begin
  loop
    dbms_output.put_line(l_value);
    if l_value = 0 then
      exit;
    else
      l_value := l_value - 1;
    end if;
  end loop;
end;

We could easily rewrite the loop using EXIT WHEN, making it more readable:

loop
  dbms_output.put_line(l_value);
  exit when l_value = 0;

  l_value := l_value - 1;
end loop;

As you can see, EXIT WHEN is merely a rewriting of an IF (condition) THEN EXIT statement.

Chapter 5 of Oracle PL/SQL Programming, fifth edition, by Steven Feuerstein is about loops.