MongoDB query array of objects in collection

Question

I have a collection, and inside this collection I have an array of objects called Degrees.

This array contains objects with keys {Uni:'',Level:'',Degree:''}, I want to be able to add to a parameter object the ability to find any document with a degree where level = 'BS', for example, regardless of what the other fields in the object contain.

I have tried so far:

{
  $elemMatch: {
    $eq: {
      Uni: {
        $exists: true,
        
      },
      Level: "BS",
      Degree: {
        $exists: true
      }
    }
  }
}

But it has not worked, any suggestions?

Joe · Accepted Answer · 2017-12-01 23:02:33Z

4

You can query the fields of the documents in the embedded array directly.

If your documents look something like

{
 _id:ObjectId("..."),
 Name: "",
 degrees: [
           {Uni:"",
            Level:"BS",
            Degree:""}
          ]
 }

You could return all documents that contain at least one 'BS' level degree with

db.collection.find({"degrees.Level":"BS"})

answered Dec 1, 2017 at 23:02

Joe

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Vishal kaushik · Accepted Answer · 2017-12-02 20:58:37Z

3

The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria.

{ <field>: { $elemMatch: { <query1>, <query2>, ... } } }

I guess this should work for you :

db.collection.find({Degrees: {$elemMatch: {level:'BS'}}})

Don't forget to replace collection with ur model name. :)

Do checkout $elemMatch documetation here : mongoDb $elemMatch

answered Dec 2, 2017 at 20:58

Vishal kaushik

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Comments

Gershom Maes · Accepted Answer · 2017-12-01 22:12:50Z

1

If I'm understanding you correctly, and assuming your collection is called degrees, it should be as simple as:

// From the mongo shell:
db.degrees.find({ Level: 'BS' });

// From javascript (assuming node's native driver):
db.collection('degrees').find({ Level: 'BS' });

If you're interested in only the first result then you can use the following:

// From the mongo shell:
db.degrees.findOne({ Level: 'BS' });

// From javascript:
db.collection('degrees').findOne({ Level: 'BS' });

answered Dec 1, 2017 at 22:12

Gershom Maes

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