text: Q:
  
  Why $lt in MongoDB doesn´t work in this query?
  
  I am developing a web platform for people who is learning languages, I have a collection for users like that:
  {
      "_id" : ObjectId("54a15e7e3453b5741a6c7be0"),
      "name" : "Miguel Lopez",
      "lng" : [ 
          {
              "ES" : 5
          }, 
          {
              "EN" : 4
          }, 
          {
              "IT" : 3
          }
      ],
      "email" : "miguel@gmail.com",
      "password" : "123456"
  }
  
  In "lng" field I save the languages that this user is learning, each language have a level between 1 and 5. To get the list of users who are learning "ES" and have level 5, I use this query:
  db.users.find({lng : {ES:5}})
  
  And it´s working perfectly, but when I want the get users who have a specific language (for example "EN") with a level less than 5, I use this query:
  db.users.find({lng : {EN:{$lt: 5}}})
  
  But this query doesn´t work, and I dont know the reason, when I try to execute this query in Robomongo I get this message: "Script executed succesfully, but there is no results to show"
  
  A:
  
  You need to use $elemMatch or dot notation
  db.users.find({lng : {$elemMatch: {EN:{$lt: 5}}}})
  db.users.find({ "lng.EN" : { "$lt" : 5 } })
  
  