title: Oracle PL/SQL string compare issue
body: <p>I have the following Oracle PL/SQL codes that may be rusty from you guys perspective: </p>
  
  <pre><code> DECLARE
   str1  varchar2(4000);
   str2  varchar2(4000);
   BEGIN
     str1:='';
     str2:='sdd';
     IF(str1&lt;&gt;str2) THEN
      dbms_output.put_line('The two strings is not equal');
     END IF;
   END;
   /
  </code></pre>
  
  <p>This is very obvious that two strings str1 and str2 are not equal, but why 'The two strings are not equal' was not printed out? Do Oracle have another common method to compare two string?</p>