Querying nested fields at any depth in MongoDB

Introduction

Sometimes data is stored inside other data. We need to find information deep inside these layers.

You want to find a friend's phone number inside their address book stored in a database.

You need to get the price of a product inside a list of product details.

You want to check if a comment inside a post has a certain word.

You want to find a user whose profile has a nested setting turned on.

Syntax

MongoDB

{ 'outer.inner.deep': value }

Use dots (.) to go inside nested fields.

Replace 'outer.inner.deep' with your actual nested field names.

Examples

Finds documents where the city inside the address is 'New York'.

MongoDB

{ 'address.city': 'New York' }

Finds products with a price of 100 inside their details.

MongoDB

{ 'product.details.price': 100 }

Finds documents where any comment's text is 'great'.

MongoDB

{ 'comments.text': 'great' }

Sample Program

This finds users whose email inside profile > contact is '[e-mail]'.

MongoDB

db.users.find({ 'profile.contact.email': '[e-mail]' })

Important Notes

If the nested field does not exist, the query will not match that document.

You can use this dot notation with other query operators like $gt, $lt, $in.

Summary

Use dot notation to reach inside nested fields.

This helps find data stored deep inside documents.

It works with any depth of nesting.