MongoDB find by multiple array items using $in?

To find documents by multiple array items in MongoDB, use the $in operator. This operator matches documents where the array field contains any of the specified values.

Syntax

db.collection.find({
    "arrayField": { $in: ["value1", "value2", "value3"] }
});

Sample Data

db.findByMultipleArrayDemo.insertMany([
    {
        "StudentFirstName": "John",
        "StudentLastName": "Smith",
        "StudentCoreSubject": ["Compiler", "Operating System", "Computer Networks"]
    },
    {
        "StudentFirstName": "Carol",
        "StudentLastName": "Taylor",
        "StudentCoreSubject": ["MongoDB", "MySQL", "SQL Server"]
    },
    {
        "StudentFirstName": "Bob",
        "StudentLastName": "Taylor",
        "StudentCoreSubject": ["MongoDB", "MySQL", "SQL Server"]
    },
    {
        "StudentFirstName": "David",
        "StudentLastName": "Johnson",
        "StudentCoreSubject": ["Compiler", "Operating System", "Computer Networks"]
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c7ef07b559dd2396bcfbfc4"),
        ObjectId("5c7ef09d559dd2396bcfbfc5"),
        ObjectId("5c7ef0c7559dd2396bcfbfc6"),
        ObjectId("5c7ef0f2559dd2396bcfbfc7")
    ]
}

Example: Find Students with Specific Subjects

Find students who study either "Compiler" or "Computer Networks" ?

db.findByMultipleArrayDemo.find({
    StudentCoreSubject: { $in: ["Compiler", "Computer Networks"] }
}).pretty();

{
    "_id": ObjectId("5c7ef07b559dd2396bcfbfc4"),
    "StudentFirstName": "John",
    "StudentLastName": "Smith",
    "StudentCoreSubject": [
        "Compiler",
        "Operating System",
        "Computer Networks"
    ]
}
{
    "_id": ObjectId("5c7ef0f2559dd2396bcfbfc7"),
    "StudentFirstName": "David",
    "StudentLastName": "Johnson",
    "StudentCoreSubject": [
        "Compiler",
        "Operating System",
        "Computer Networks"
    ]
}

Key Points

• The $in operator returns documents if the array contains at least one matching value.
• Use $all operator if you need documents containing all specified values.
• Works with both array fields and single value fields.

Conclusion

The $in operator efficiently finds documents where array fields contain any of the specified values. This is ideal for filtering documents based on multiple possible array elements.