MongoDB query to fetch only the "Name" field based on roles?

To fetch only the "Name" field based on specific roles in MongoDB, use the aggregation framework with $group, $setIsSubset, and $match operators. This approach filters documents by comparing their roles against a target role set.

Syntax

db.collection.aggregate([
    { $group: { _id: "$Name", "types": { $addToSet: "$Type" } } },
    { $project: { _id: 1, "types": 1, "isSubset": { $setIsSubset: [["TargetRole"], "$types"] } } },
    { $match: { "isSubset": false } },
    { $group: { _id: "$isSubset", "Name": { $push: "$_id" } } },
    { $project: { "_id": 0, "Name": 1 } },
    { $unwind: "$Name" }
]);

Sample Data

db.demo532.insertMany([
    { "Name": "Chris", "Type": "Admin" },
    { "Name": "David", "Type": "Guest" },
    { "Name": "Bob", "Type": "User" }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e8b4a9def4dcbee04fbbbf9"),
        ObjectId("5e8b4aa3ef4dcbee04fbbbfa"),
        ObjectId("5e8b4ab0ef4dcbee04fbbbfb")
    ]
}

Display all documents ?

db.demo532.find();

{ "_id": ObjectId("5e8b4a9def4dcbee04fbbbf9"), "Name": "Chris", "Type": "Admin" }
{ "_id": ObjectId("5e8b4aa3ef4dcbee04fbbbfa"), "Name": "David", "Type": "Guest" }
{ "_id": ObjectId("5e8b4ab0ef4dcbee04fbbbfb"), "Name": "Bob", "Type": "User" }

Example: Fetch Names Excluding Admin Role

Get names of users who do NOT have "Admin" role ?

db.demo532.aggregate([
    { $group: { _id: "$Name", "types": { $addToSet: "$Type" } } },
    { $project: { _id: 1, "types": 1, "isSubset": { $setIsSubset: [["Admin"], "$types"] } } },
    { $match: { "isSubset": false } },
    { $group: { _id: "$isSubset", "Name": { $push: "$_id" } } },
    { $project: { "_id": 0, "Name": 1 } },
    { $unwind: "$Name" }
]);

{ "Name": "David" }
{ "Name": "Bob" }

How It Works

• $group groups documents by Name and creates a types array
• $setIsSubset checks if ["Admin"] is a subset of each user's types
• $match filters users where isSubset is false (non-Admin users)
• $unwind flattens the Name array to individual documents

Conclusion

The aggregation pipeline with $setIsSubset efficiently filters documents by role comparison. This method returns only the Name field for users who don't match the specified role criteria.