Find the document by field name with a specific value in MongoDB?

To find documents by field name with a specific value in MongoDB, you can use the $exists operator to check if a field exists, or use dot notation to match specific field values in nested documents.

Syntax

// Check if field exists
db.collection.find({"fieldName": {$exists: true}})

// Find by specific value in nested field
db.collection.find({"parent.child": "specificValue"})

Sample Data

db.findByFieldName.insertMany([
    {
        "Client": {
            "ClientDetails": {
                "ClientName": "Larry",
                "ClientAge": 29
            },
            "ClientProjectDetails": {
                "ProjectName": "Online Book Store",
                "TeamSize": 10,
                "TechnologyUsed": "Spring Boot"
            }
        }
    },
    {
        "Client": {
            "ClientDetails": {
                "ClientName": "Chris",
                "ClientAge": 27
            },
            "ClientEducationDetails": {
                "isEducated": true,
                "CollegeName": "M.I.T."
            }
        }
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("..."),
        ObjectId("...")
    ]
}

Example 1: Find Documents Where Field Exists

Find all documents that have the "ClientProjectDetails" field ?

db.findByFieldName.find({"Client.ClientProjectDetails": {$exists: true}});

{
    "_id": ObjectId("5c9e93b2d628fa4220163b64"),
    "Client": {
        "ClientDetails": {
            "ClientName": "Larry",
            "ClientAge": 29
        },
        "ClientProjectDetails": {
            "ProjectName": "Online Book Store",
            "TeamSize": 10,
            "TechnologyUsed": "Spring Boot"
        }
    }
}

Example 2: Find by Specific Field Value

Find documents where ClientName is "Chris" ?

db.findByFieldName.find({"Client.ClientDetails.ClientName": "Chris"});

{
    "_id": ObjectId("5c9e9421d628fa4220163b65"),
    "Client": {
        "ClientDetails": {
            "ClientName": "Chris",
            "ClientAge": 27
        },
        "ClientEducationDetails": {
            "isEducated": true,
            "CollegeName": "M.I.T."
        }
    }
}

Key Points

• $exists: true finds documents where the specified field exists
• $exists: false finds documents where the field does not exist
• Use dot notation to access nested fields: "parent.child.field"

Conclusion

Use $exists to find documents by field presence, or dot notation with specific values to match nested field content. Both approaches help filter documents based on field structure and values.