CODEWITHSUNDEEP
node.jsmongodbmongoose
Pavan Boro
Pavan Boro

Reputation: 95

How do I query the 2 collections in mongoose?

I have 2 collections namely eventPart and Participants.

eventPart:{
   {
    "_id" : ObjectId("5b62676ba5419449046a26c4"),
    "rollNo" : "15K21A0528",
    "eventName" : "Ebullienza",
    "team" : 68,
     "__v" : 0
},{
    "_id" : ObjectId("5b62676ba5419449046a26c5"),
    "rollNo" : "15G11A0518",
    "eventName" : "Ebullienza",
    "team" : 68,
    "__v" : 0}
}

Participants : {
   {
     "_id" : ObjectId("5b62626d9306a610e36aca95"),
     "rollNo" : "15S11A0528",
     "name" : "Pavan Boro",
     "email" : "[email protected]",
     "mobile" : NumberLong(6700332950),
     "branch" : "CSE",
     "section" : "A",
     "year" : 4
}, {
     "_id" : ObjectId("5b62633d9306a610e36acae1"),
     "rollNo" : "15S11A0518",
     "name" : "Manoj",
     "email" : "[email protected]",
     "mobile" : NumberLong(9700332910),
     "branch" : "CSE",
     "section" : "A",
     "year" : 4
}}

I want to query the database with eventName in eventPart along with data in Participant collection.

Ex: With eventName : 'Ebullienza' I want to fetch all the details that is related to eventName: 'Ebullienza' in Participants collection.

I have tried collecting the rollNo from eventPart and using it for in Participants collection. But I get stuck in collecting the rollNo in array

 var rollNumber = new Array();
 EventPart.find({'eventName':'Ebullineza'}).then(function(a){
    a.forEach(function(roll){
        rollNumber.push(roll.rollNo);
  });
});
console.log(rollNumber); // prints [] - empty array

rollNumber is printed as [].

I think there could be a more efficient way of query 2 collections in mongoose.

Thanks.

Upvotes: 0

Views: 47

Answers (2)

Daphoque
Daphoque

Reputation: 4678

print your array in the callback... otherwise he is printed before the end of execution of your find 

 var rollNumber = new Array();
 EventPart.find({'eventName':'Ebullineza'}).then(function(a){
    a.forEach(function(roll){
        rollNumber.push(roll.rollNo);
  });
  console.log(rollNumber); // prints [] - empty array
});

Upvotes: 0

Senthur Deva
Senthur Deva

Reputation: 787

use $lookup

db.eventPart.aggregate([
    { "$match": { "eventName": "Ebullienza" } },
    {
        "$lookup": {
            "from": "Participants",
            "localField": "rollNo",
            "foreignField": "rollNo",
            "as": "Participants"
        }
    }
])

Upvotes: 1

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