title: MySQL 'AND' not working
body: <p>I Have the following query: </p>
  
  <pre><code>SELECT * FROM students 
  WHERE gwid NOT IN (
      SELECT gwid FROM attendance 
      WHERE((date='160126') AND (classid = 'm1100'))
  )
  </code></pre>
  
  <p>The query runs without an error but it still shows rows in which the classid is not m1100. Please look at the same result below:</p>
  
  <p><a href="https://i.stack.imgur.com/ZunFo.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZunFo.jpg" alt=""></a></p>