MongoDB query to find on the basis of true or false values

To find documents based on true or false values in MongoDB, use the $exists operator with dot notation to check field presence or use direct boolean value matching.

Syntax

db.collection.find({"field": { $exists: true/false }});
db.collection.find({"booleanField": true/false});

Sample Data

db.demo367.insertMany([
    {
        "Id": "102",
        "details": [
            { "Name": "David" },
            { "Age": 23, "CountryName": "UK" }
        ],
        "isMarried": false
    },
    {
        "Id": "101",
        "details": [
            { "Name": "Chris", "Subject": ["MySQL"] },
            { "Age": 21, "CountryName": "US" }
        ],
        "isMarried": true
    }
]);

Method 1: Using $exists to Check Field Presence

Find documents where the nested "Subject" field does not exist ?

db.demo367.find({"details.Subject": { $exists: false }});

{
    "_id": ObjectId("5e57e0b62ae06a1609a00ae8"),
    "Id": "102",
    "details": [
        { "Name": "David" },
        { "Age": 23, "CountryName": "UK" }
    ],
    "isMarried": false
}

Method 2: Direct Boolean Value Matching

Find documents where "isMarried" is true ?

db.demo367.find({"isMarried": true});

{
    "_id": ObjectId("5e57e0be2ae06a1609a00ae9"),
    "Id": "101",
    "details": [
        { "Name": "Chris", "Subject": ["MySQL"] },
        { "Age": 21, "CountryName": "US" }
    ],
    "isMarried": true
}

Key Points

• $exists: false finds documents where the specified field is missing
• $exists: true finds documents where the specified field is present
• Use dot notation for nested field queries
• Direct boolean matching queries the actual field value

Conclusion

Use $exists to check field presence and direct boolean matching to query true/false values. Combine with dot notation for nested field queries in complex document structures.