Inner Queries of References

[Alex Price]

Hey,

I am trying to figure out how to do an Innery Query. Here are my Schemas:

var Course = mongoose.model('Course',new Schema({

  createdAt: Date,

  updatedAt: { type: Date, 'default': Date.now },

  city: String,

  country: String,

  description: String,

  latitude: String,

  longitude: String,

  name: String,

  status: Boolean,

  Professor_idProfessor:{ type: Schema.Types.ObjectId, ref: 'User' },

  School_idSchool:{ type: Schema.Types.ObjectId, ref: 'School'}

}));

var Section = mongoose.model('Section',new Schema({

  createdAt: Date,

  updatedAt: { type: Date, 'default': Date.now },  

  days: String,

  name: String,

  status: Boolean,

  studentCount: Number,

  time: String,
  Course_idCourse:{ type: Schema.Types.ObjectId, ref: 'Course' }
}));

I want to find all sections who's parent course have the name 'Math'. I figured it would work like this:
Section.find({'Course_idCourse.name':'Math'},function(err,obj){
console.log(err,obj);
});

This does not work though. Any suggestions?

[Jason Crawford]

That query would work if you had an embedded document. But when these are two different collections, you're basically trying to do a join.

As I understand it, there are no joins in MongoDB. You can't do a single query and get data from two different collections. You have to query the first, then separately query the second.

However, Mongoose can help you with this, using population:

http://mongoosejs.com/docs/populate.html

Hope that helps,

Jason

--
Blog: http://blog.jasoncrawford.org  |  Twitter: @jasoncrawford

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