title: The NOT IN with NULL values dilemma in ORACLE SQL
body: <p>When I used this code</p>
  
  <pre><code>WHEN col1 NOT IN (SELECT col2 FROM table_name) THEN 'something'
  </code></pre>
  
  <p>it didn't give the expected results knowing that col2 contains a NULL value, Why did this happened ? Does using IN with NULL values messes with data stored in memory or what?</p>