Restrict returned data in MongoDB to display only specific values from documents

To restrict returned data in MongoDB, use the projection parameter in the find() method. Use values 1 to include fields and 0 to exclude fields from the query results.

Syntax

db.collection.find(query, projection)

Where:

• query − Filter criteria (empty {} for all documents)
• projection − Fields to include (1) or exclude (0)

Sample Data

Let us create a collection with documents −

db.demo330.insertMany([
    {"Id": 101, "Name": "Chris", "Age": 21},
    {"Id": 102, "Name": "Sam", "Age": 24},
    {"Id": 103, "Name": "David", "Age": 28},
    {"Id": 104, "Name": "Bob", "Age": 23}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e52149ff8647eb59e562081"),
        ObjectId("5e5214aaf8647eb59e562082"),
        ObjectId("5e5214b3f8647eb59e562083"),
        ObjectId("5e5214bdf8647eb59e562084")
    ]
}

Display all documents from a collection with the help of find() method −

db.demo330.find();

{ "_id" : ObjectId("5e52149ff8647eb59e562081"), "Id" : 101, "Name" : "Chris", "Age" : 21 }
{ "_id" : ObjectId("5e5214aaf8647eb59e562082"), "Id" : 102, "Name" : "Sam", "Age" : 24 }
{ "_id" : ObjectId("5e5214b3f8647eb59e562083"), "Id" : 103, "Name" : "David", "Age" : 28 }
{ "_id" : ObjectId("5e5214bdf8647eb59e562084"), "Id" : 104, "Name" : "Bob", "Age" : 23 }

Example 1: Include Only Specific Fields

Show only the "Name" field by setting it to 1 −

db.demo330.find({}, {Name: 1});

{ "_id" : ObjectId("5e52149ff8647eb59e562081"), "Name" : "Chris" }
{ "_id" : ObjectId("5e5214aaf8647eb59e562082"), "Name" : "Sam" }
{ "_id" : ObjectId("5e5214b3f8647eb59e562083"), "Name" : "David" }
{ "_id" : ObjectId("5e5214bdf8647eb59e562084"), "Name" : "Bob" }

Example 2: Exclude the _id Field

Display only "Name" and "Age" without the default "_id" field −

db.demo330.find({}, {_id: 0, Name: 1, Age: 1});

{ "Name" : "Chris", "Age" : 21 }
{ "Name" : "Sam", "Age" : 24 }
{ "Name" : "David", "Age" : 28 }
{ "Name" : "Bob", "Age" : 23 }

Key Points

• The _id field is always included by default unless explicitly excluded with _id: 0.
• You cannot mix inclusion (1) and exclusion (0) in the same projection, except for _id.
• Empty projection {} returns all fields.

Conclusion

MongoDB projection allows you to control which fields are returned in query results. Use 1 to include specific fields and 0 to exclude unwanted data, optimizing query performance and reducing network traffic.