MongoDB allows for complex data structures by supporting embedded or nested documents. This feature is powerful for modeling real-world entities and their relationships directly within a single document. Querying these embedded documents requires a good understanding of MongoDB's querying capabilities.

In this lesson, we will explore how to query embedded or nested documents in MongoDB.

Basic Query on Embedded Documents

When querying embedded documents, you need to use dot notation to specify the field within the embedded document.

Syntax

db.collection.find(
  { "embeddedField.subField": <value> }
)

In the above syntax, embeddedField is a parent document, and subField is a nested document.

Examples

1. Inserting a Simple Embedded Document: To insert the document into a MongoDB collection, you can use the insertOne() method. Here’s how you can do it:

   db.collection.insertOne({
     name: "John Doe",
     address: {
   	street: "123 Main St",
   	city: "Anytown",
   	zipcode: "12345"
     }
   })

2. Querying a Simple Embedded Document

   To query documents where the city in the address is "Anytown":

   db.users.find({ "address.city": "Anytown" })

   This command retrieves all documents where the address.city field is "Anytown".

3. Querying Multiple Fields in Embedded Documents

   To query documents where the city is "Anytown" and the zipcode is "12345":

   db.users.find({ "address.city": "Anytown", "address.zipcode": "12345" })

   This command retrieves all documents where both the address.city field is "Anytown" and the address.zipcode field is "12345".