MongooseJS - How to find the element with the maximum value?

Question

I am using MongoDB , MongooseJS and Nodejs.

I have a Collection ( called Member ) with the following Fields -

Country_id , Member_id , Name, Score

I want to write a query which returns the Member with the max Score where Country id = 10

I couldnt find suitable documentation for this in MongooseJS.

I found this at StackOVerflow ( this is MongoDB code )

Model.findOne({ field1 : 1 }).sort(last_mod, 1).run( function(err, doc) {      var max = doc.last_mod; }); 

But how do I translate the same to MongooseJS ?

Answer 1

Member   .findOne({ country_id: 10 })   .sort('-score')  // give me the max   .exec(function (err, member) {      // your callback code    }); 

Check the mongoose docs for querying, they are pretty good.

If you dont't want to write the same code again you could also add a static method to your Member model like this:

memberSchema.statics.findMax = function (callback) {    this.findOne({ country_id: 10 }) // 'this' now refers to the Member class     .sort('-score')     .exec(callback); } 

And call it later via Member.findMax(callback)

Answer 2

You do not need Mongoose documentation to do this. Plain MongoDb will do the job.

Assume you have your Member collection:

{ "_id" : ObjectId("527619d6e964aa5d2bdca6e2"), "country_id" : 10, "name" : "tes2t", "score" : 15 } { "_id" : ObjectId("527619cfe964aa5d2bdca6e1"), "country_id" : 10, "name" : "test", "score" : 5 } { "_id" : ObjectId("527619e1e964aa5d2bdca6e3"), "country_id" : 10, "name" : "tes5t", "score" : -6 } { "_id" : ObjectId("527619e1e964aa5d2bdcd6f3"), "country_id" : 8, "name" : "tes5t", "score" : 24 } 

The following query will return you a cursor to the document, you are looking for:

 db.Member.find({country_id : 10}).sort({score : -1}).limit(1)