Find inside a hash MongoDB?

To find inside a hash (embedded document) in MongoDB, use dot notation to access nested fields. This allows you to query specific fields within embedded documents using the format "parentField.childField".

Syntax

db.collection.find({
    "embeddedDocument.field": "value"
});

Sample Data

Let us create a collection with documents containing embedded ClientDetails ?

db.hashDemo.insertMany([
    {
        "ClientName": "Larry",
        "ClientAge": 23,
        "ClientDetails": {
            "isEducated": true,
            "ClientProject": "University Management"
        }
    },
    {
        "ClientName": "Chris", 
        "ClientAge": 26,
        "ClientDetails": {
            "isEducated": false,
            "ClientProject": "Online Book Store"
        }
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5ca1ef1266324ffac2a7dc5e"),
        ObjectId("5ca1ef7766324ffac2a7dc5f")
    ]
}

Display All Documents

db.hashDemo.find().pretty();

{
    "_id": ObjectId("5ca1ef1266324ffac2a7dc5e"),
    "ClientName": "Larry",
    "ClientAge": 23,
    "ClientDetails": {
        "isEducated": true,
        "ClientProject": "University Management"
    }
}
{
    "_id": ObjectId("5ca1ef7766324ffac2a7dc5f"),
    "ClientName": "Chris",
    "ClientAge": 26,
    "ClientDetails": {
        "isEducated": false,
        "ClientProject": "Online Book Store"
    }
}

Example: Query Embedded Fields

Find clients who are not educated and work on "Online Book Store" project ?

db.hashDemo.find({
    "ClientDetails.isEducated": false,
    "ClientDetails.ClientProject": "Online Book Store"
}).pretty();

{
    "_id": ObjectId("5ca1ef7766324ffac2a7dc5f"),
    "ClientName": "Chris",
    "ClientAge": 26,
    "ClientDetails": {
        "isEducated": false,
        "ClientProject": "Online Book Store"
    }
}

Conclusion

Use dot notation to query nested fields in MongoDB embedded documents. This enables precise filtering based on specific fields within hash-like structures without retrieving the entire document first.