How to implement MongoDB $or operator

The $or operator in MongoDB performs a logical OR operation on an array of expressions and returns documents that match at least one of the specified conditions.

Syntax

db.collection.find({
    $or: [
        { "field1": value1 },
        { "field2": value2 }
    ]
});

Create Sample Data

db.orOperatorDemo.insertMany([
    { "StudentNames": ["John", "Carol", "Sam"] },
    { "StudentNames": ["Robert", "Chris", "David"] },
    { "StudentNames": ["John"] }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5cd6b80a6d78f205348bc61b"),
        ObjectId("5cd6b8266d78f205348bc61c"),
        ObjectId("5cd6b8346d78f205348bc61d")
    ]
}

View Sample Data

db.orOperatorDemo.find().pretty();

{
    "_id": ObjectId("5cd6b80a6d78f205348bc61b"),
    "StudentNames": [
        "John",
        "Carol",
        "Sam"
    ]
}
{
    "_id": ObjectId("5cd6b8266d78f205348bc61c"),
    "StudentNames": [
        "Robert",
        "Chris",
        "David"
    ]
}
{
    "_id": ObjectId("5cd6b8346d78f205348bc61d"),
    "StudentNames": [
        "John"
    ]
}

Example: Using $or Operator

Find documents where StudentNames contains either "Carol" OR "John" ?

db.orOperatorDemo.find({
    $or: [
        { "StudentNames": "Carol" },
        { "StudentNames": "John" }
    ]
}).pretty();

{
    "_id": ObjectId("5cd6b80a6d78f205348bc61b"),
    "StudentNames": [
        "John",
        "Carol",
        "Sam"
    ]
}
{
    "_id": ObjectId("5cd6b8346d78f205348bc61d"),
    "StudentNames": [
        "John"
    ]
}

Key Points

• The $or operator accepts an array of expressions
• Returns documents that match any one of the conditions
• Each condition in the array is evaluated independently

Conclusion

The $or operator provides flexible querying by matching documents against multiple conditions. Use it when you need to retrieve documents that satisfy at least one of several criteria.