how to implement the function like left join of mysql in mongoose - node.js

Question

I am going to implement the function like left join of mysql in mongoose.
the date is
var mongoose = require('mongoose')
, Schema = mongoose.Schema
var personSchema = Schema({
_id : Number,
name : String
});
var storySchema = Schema({
_creator : { type: Number, ref: 'Person' },
title : String
});
var personProfile = Schema({
userid : {type: Number, ref: 'Person'},
birthday: Date,
profilelink: String,
email: String
});
var Story = mongoose.model('Story', storySchema);
var Person = mongoose.model('Person', personSchema);
var personProfile = mongoose.model('Personprofile', personProfile );
I am going to display the Story model with the user profile.
We have to get the profile info with the _creator of story and the userid of personProfile
How can I get the info using mongoose query?
Thanks Nelis

Answer 1

What your are trying to do is not possible because there is no join statement on mongodb.
You can achieve this in two ways:
1 - By DBRefs: Changing your Schema to one that include all the user info and do not split them in two different schemas as you are doing, see denormalized. Then you can use the Population function to get all the persons data.
2 - By Manual references: The second solution is to make a second call to the database getting the personProfile data using the userid as a filter.
Example 1:
This way you can get all persons data without a second call to the database.
var personSchema = Schema({
_id : Number,
name : String,
birthday: Date,
profilelink: String,
email: String
});
var storySchema = Schema({
_creator : { type : Schema.Types.ObjectId, ref: 'Person' },
title : String
});
Story
.find()
.populate(['_creator'])
.exec(function(err, stories) {
//do your stuff here
}
Notice that I'm using the type Schema.Types.ObjectId and not the Number. This way, you can assign a new value to _creator passing either the _id or the person object and the mongoose will convert the object to its _id. For example, you can post something like
{
_creator : {
_id : 123123123123,
name : 'Foo',
birthday: '0000-00-00',
profilelink: 'http://foo.bar',
email: 'foo#bar.com'
},
title : 'Mr'
}
... and the mongoose will convert to
{
_creator : 123123123123,
title : 'Mr'
}
Example 2:
This way your data still normalized and you can get all the persons data with a second call.
Story
.find()
.exec(function(err, stories) {
var arrayLength = stories.length;
for (var i = 0; i < arrayLength; i++) {
var story = stories[i];
personProfile.findById(story._creator, function (err, person) {
story._creator = person;
}
};
// do your stuff here
}