 <p><code>''</code> is again <code>NULL</code> in Oracle. because Oracle doesnt support empty Strings just like Other High Level languages or DBMS..</p> <p>You need to look for NULL values using <code>IS NULL</code> or <code>IS NOT NULL</code></p> <p>No, other relational operators work against <code>NULL</code>, though it is syntactically valid. <a href="http://sqlfiddle.com/#!4/d41d8/36233" rel="nofollow">SQLFiddle Demo</a></p> <p>It has to be,</p> <pre><code>select * from example_so where mycol IS NULL </code></pre> <p><strong>EDIT:</strong> As per <a href="http://docs.oracle.com/cd/B19306_01/server.102/b14200/sql_elements005.htm" rel="nofollow">Docs</a></p> <blockquote> <p>Oracle Database currently treats a character value with a length of zero as null. However, this may not continue to be true in future releases, and Oracle recommends that you do not treat empty strings the same as nulls.</p> </blockquote>