Dot notation into nested objects

To reach a field inside a sub-document, name the path and quote it. There is no join and no special operator - "address.city" is just a field name that happens to contain a dot.

Given:

{
  name: "Denish",

  address: {
    city: "Surat",
    country: "India"
  }
}

Query:

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

The important concept is dot notation.

You will use it constantly.