title: MongoDB : Multi Update with where condition
body: <p>Requirement: Get All documents where point &lt; 90 and increment 'point' by +20
  Data: </p>
  
  <pre><code> { "_id" : 1, "student" : 1, "type" : "exam", "point" : 115 }
      { "_id" : 2, "student" : 2, "type" : "exam", "point" : 85 }
      { "_id" : 3, "student" : 3, "type" : "exam", "point" : 115 }
  
  Query tried : 
  // query below 
  </code></pre>
  
  <p>db.points.update({},{$inc:{point:20},point:{lt:110}},{multi:true})</p>
  
  <pre><code>On executing : fn[0] == '$'is seen and query has not affected any changes.
  </code></pre>