title: Mongoose Schema for SMS Log
body: <p>My app sends SMS to students and I need to save sms history
  I want to find both</p>
  
  <ol>
  <li>Student List by SMS Id</li>
  <li>List of sms sent to student</li>
  </ol>
  
  <p>Which is Better Approach:
   1. SMS History Schema</p>
  
  <pre><code>{
  date: String,
  smsCount: Number,
  studentIds: Array[Number]   
  }
  </code></pre>
  
  <p>2. SMS id in student Column</p>
  
  <pre><code>{
  name: String;
  rollNo: Number;
  smsIds: Array[Number]
  }
  </code></pre>
  
  <p>3. Seperate Log Schema</p>
  
  <pre><code> {
     smsId: Number,
     userId: Number,
     date:   Date
   }
  </code></pre>
  
  <p>Which approach is better?</p>