title: Use more than one schema per collection on mongodb
body: <p>I wanted to use more than one schema per collection in mongodb , how to use it....?<br>
  It gives me this error when I try to run it:
  <br><br>Error: </p>
  
  <blockquote>
    <p>OverwriteModelError: Cannot overwrite <code>allUsers</code> model once compiled.
    <br> OverwriteModelError: Cannot overwrite <code>checkInOut</code> model once compiled.</p>
  </blockquote>
  
  <p><br>Heres my schema.js</p>
  
  <pre><code>   var mongoose = require('mongoose');
  
        var Schema = mongoose.Schema
            , ObjectId = Schema.ObjectId;
  
     var checkInInfoSchema= new Schema({
         name:String,
         loginSerialId:Number
     });
  
  
     var loginUserSchema = new Schema({
            sn : { type: Number, unique:true }
            ,uname: {type:String, unique:true}
            ,pass:String
        });
  
     var registerUserSchema = new Schema({
         sn : { type: Number, unique:true }
         , name: String   //his/her name
         ,pass:String,
         companyKey:{type:String},
         uname:{type:String,unique:true}
     });
  
  
  
     var checkInOutSchema = new Schema({
         uname: String
         ,companyKey:String
         ,task:String
         ,inTime:String
         ,outTime:String
         ,date:{type:String}
         ,serialId:{type:Number,unique:true}
         ,online:Boolean
     });
  
     //Different schema for same collection "allUsers"        
     var allUser=mongoose.model('allUsers',loginUserSchema);        
     var registerUser=mongoose.model('allUsers',registerUserSchema);
  
      //Different schema for same collection "checkInOut"
     var checkInOut=mongoose.model('checkInOut',checkInOutSchema);
     var checkInInfo=mongoose.model('checkInOut',checkInInfoSchema);
  
     module.exports={
  
         allUser:allUser, 
         registerUser:registerUser,
  
         checkInOut:checkInOut,
         checkInInfo:checkInInfo
     };
  </code></pre>