title: How to join databases in mongoDB and fetch the required result
body: <p>I have somewhat of the following type of database - </p>
  
  <pre><code>var school= mongoose.model('School' ,{
      name : { type : String, minlength : 1, trim : true },
      email : { type : String, trim : true },
      password : { type : String, minlength : 8, },
      mobile : { type : Number, minlength : true },
      address : { type : String },
      description : { type : String },
      student : { type : Array },
  });
  </code></pre>
  
  <p>My site is home to many schools so the students should be able to see only the students of the same school. For this I have created a different table for the students and entering their unique values in the <strong>Student Array in School DB</strong> along with the respective student DB. How should I be able to fetch <strong>all the Student's data</strong>  if i have student array from School DB.....</p>