Welcome! In this lesson, we’ll explore how to query nested fields and arrays in MongoDB. Additionally, we will cover two comparison operators, $in and $nin, that were not discussed in the previous lesson. Let's get started!

When documents contain nested fields, like sub-documents, querying can be achieved using dot notation. For example, consider a document in our comic_book_store_db database:

Let's say we want to find a comic book where the writer's name is "Stan Lee". Here's how you do it:

This query searches within the sub-document writer for the field name. Note that writer.name should be in quotes; otherwise, the . will cause an error in your query.

Arrays are common in many documents. Our comic_book_store_db has fields like genres and characters, which are arrays. Here's an example of a document containing arrays:

Here are some examples of querying arrays in MongoDB:

The $in operator is used to match any value within an array of specific values. If we want a comic book that belongs to either 'Action' or 'Adventure' genres:

Conversely, the $nin operator matches any value that does not exist in the specified array. To find a comic book where the writer's nationality is not "American" or "British":

In this lesson, we've explored querying nested fields and arrays within MongoDB documents. We used dot notation to dig into sub-documents and arrays, and powerful operators like $in and $nin to refine our queries. Practice these techniques to enhance your MongoDB querying skills and easily navigate complex document structures. Keep experimenting!