How to remove primary key from MongoDB?

To remove the primary key (_id field) from query results in MongoDB, use projection with the _id: 0 option in the find() method. This excludes the _id field from the returned documents without deleting it from the database.

Syntax

db.collection.find({}, {_id: 0});
db.collection.find({}, {_id: 0, field1: 1, field2: 1});

Sample Data

db.demo471.insertMany([
    {"ClientId": 101, "ClientName": "Chris"},
    {"ClientId": 102, "ClientName": "Bob"},
    {"ClientId": 103, "ClientName": "David"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e805711b0f3fa88e2279077"),
        ObjectId("5e80571db0f3fa88e2279078"),
        ObjectId("5e805724b0f3fa88e2279079")
    ]
}

View Default Documents

Display all documents with the default _id field ?

db.demo471.find();

{ "_id": ObjectId("5e805711b0f3fa88e2279077"), "ClientId": 101, "ClientName": "Chris" }
{ "_id": ObjectId("5e80571db0f3fa88e2279078"), "ClientId": 102, "ClientName": "Bob" }
{ "_id": ObjectId("5e805724b0f3fa88e2279079"), "ClientId": 103, "ClientName": "David" }

Method 1: Exclude Only _id Field

Remove the primary key (_id) while keeping all other fields ?

db.demo471.find({}, {_id: 0});

{ "ClientId": 101, "ClientName": "Chris" }
{ "ClientId": 102, "ClientName": "Bob" }
{ "ClientId": 103, "ClientName": "David" }

Method 2: Exclude Multiple Fields

Remove both _id and ClientId fields ?

db.demo471.find({}, {_id: 0, ClientId: 0});

{ "ClientName": "Chris" }
{ "ClientName": "Bob" }
{ "ClientName": "David" }

Key Points

• Setting _id: 0 in projection excludes the _id field from query results
• The _id field remains in the database − only hidden from the output
• You can exclude multiple fields by setting each to 0 in the projection object

Conclusion

Use projection with {_id: 0} to remove the primary key from MongoDB query results. This approach hides the _id field without permanently deleting it from your documents.