Query to retrieve multiple items in an array in MongoDB?

To retrieve multiple items in an array in MongoDB, use the aggregation framework with $unwind, $match, and $group operators to filter and reconstruct array elements based on specific criteria.

Syntax

db.collection.aggregate([
    { $unwind: "$arrayField" },
    { $match: { "arrayField.field": { $in: [values] } } },
    { $group: { "_id": "$_id", "arrayField": { $push: "$arrayField" } } }
]);

Sample Data

db.retrieveMultipleDemo.insertOne({
    "UserDetails": [
        { "_id": "101", "UserName": "John", "UserAge": 23 },
        { "_id": "102", "UserName": "Carol", "UserAge": 21 },
        { "_id": "103", "UserName": "David", "UserAge": 23 },
        { "_id": "104", "UserName": "Sam", "UserAge": 25 }
    ]
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5cd40c85edc6604c74817cf0")
}

Display All Documents

db.retrieveMultipleDemo.find().pretty();

{
    "_id": ObjectId("5cd40c85edc6604c74817cf0"),
    "UserDetails": [
        {
            "_id": "101",
            "UserName": "John",
            "UserAge": 23
        },
        {
            "_id": "102",
            "UserName": "Carol",
            "UserAge": 21
        },
        {
            "_id": "103",
            "UserName": "David",
            "UserAge": 23
        },
        {
            "_id": "104",
            "UserName": "Sam",
            "UserAge": 25
        }
    ]
}

Retrieve Multiple Items with Age Filter

Query to retrieve users with age 23 ?

db.retrieveMultipleDemo.aggregate([
    { $unwind: "$UserDetails" },
    { $match: { "UserDetails.UserAge": 23 } },
    { $group: { "_id": "$_id", "UserDetails": { $push: "$UserDetails" } } },
    { $project: { "_id": 0, "UserDetails": 1 } }
]);

{
    "UserDetails": [
        { "_id": "101", "UserName": "John", "UserAge": 23 },
        { "_id": "103", "UserName": "David", "UserAge": 23 }
    ]
}

How It Works

• $unwind − Deconstructs the array into separate documents
• $match − Filters documents based on array element criteria
• $group − Reconstructs the array with matching elements only
• $project − Shapes the final output format

Conclusion

Use MongoDB's aggregation pipeline to retrieve multiple filtered items from arrays. The combination of $unwind, $match, and $group provides powerful array filtering capabilities.