MongoDB equivalent of WHERE IN(1,2,...)?

The MongoDB equivalent of SQL's WHERE IN(1,2,...) clause is the $in operator. This operator allows you to match documents where a field value equals any value in a specified array.

Syntax

db.collectionName.find({
    fieldName: { $in: [value1, value2, value3, ...] }
});

Sample Data

Let us create a collection with student documents ?

db.whereInDemo.insertMany([
    { "StudentName": "John", "StudentMathScore": 57 },
    { "StudentName": "Larry", "StudentMathScore": 89 },
    { "StudentName": "Chris", "StudentMathScore": 98 },
    { "StudentName": "Robert", "StudentMathScore": 99 },
    { "StudentName": "Bob", "StudentMathScore": 97 }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5ca281ec6304881c5ce84ba5"),
        ObjectId("5ca281f56304881c5ce84ba6"),
        ObjectId("5ca281fd6304881c5ce84ba7"),
        ObjectId("5ca2820a6304881c5ce84ba8"),
        ObjectId("5ca282206304881c5ce84ba9")
    ]
}

Example: Using $in Operator

Find students with math scores of 97, 98, or 99 ?

db.whereInDemo.find({
    StudentMathScore: { $in: [97, 98, 99] }
});

{
    "_id": ObjectId("5ca281fd6304881c5ce84ba7"),
    "StudentName": "Chris",
    "StudentMathScore": 98
}
{
    "_id": ObjectId("5ca2820a6304881c5ce84ba8"),
    "StudentName": "Robert",
    "StudentMathScore": 99
}
{
    "_id": ObjectId("5ca282206304881c5ce84ba9"),
    "StudentName": "Bob",
    "StudentMathScore": 97
}

Key Points

• The $in operator matches documents where the field value equals any value in the array.
• It works with numbers, strings, dates, and other data types.
• Use $nin for the opposite operation (NOT IN).

Conclusion

MongoDB's $in operator provides the same functionality as SQL's WHERE IN clause. It efficiently matches documents where a field contains any value from a specified array of options.