title: Sequelize raw mysql query returning null fields
body: <p>I have an app that asks users multiple questions. The goal is to not display a question that the user has already answered. So if Bob answers question X he won't ever see it. However, Sally would see question X if she hasn't already answered it.</p>
  
  <p>I have a MySQL query that works just fine inside my query editor. The query joins two tables and returns a question that doesn't match the provided username string or if that username is null (meaning the question hasn't been answered). The problem is inside sequelize if a username string is null the query returns null fields but if a question has been answered by another username it will display the question. </p>
  
  <p>Here is my working query:</p>
  
  <pre><code>select * from questions 
  left join responses on responses.QuestionId = questions.id 
  where responses.username &lt;&gt; 'username string' or responses.username is null
  order by rand() limit 1;
  </code></pre>
  
  <p>Here is my sequelize query:</p>
  
  <pre><code>_sequelize.query(
  'select * from questions ' +
  'left join responses on responses.QuestionId = questions.id ' +
  'where responses.username &lt;&gt; "' + req.query.name + '" or responses.username  is null ' +
  'order by rand() ' +
  'limit 1',
  {model : models.Responses})
  </code></pre>