Take your MongoDB queries to the next level! This tutorial shows you exactly how to use the powerful operators $in, $nin, and $expr to find specific data in your database.

What you will learn:

$in (In Array): How to find documents where a field's value matches any value in a list (e.g., find all users whose city is "New York" OR "London").

$nin (Not In Array): The opposite of $in. How to find documents where a field's value is not in a list (e.g., find all products that are NOT in the "Electronics" or "Clothing" categories).

$expr (Expression): The secret weapon! How to use $expr to compare two different fields within the same document (e.g., find all items where "quantity_sold" is greater than "quantity_in_stock").

Example Query (Using $expr): db.inventory.find({ $expr: { $gt: [ "$sold", "$in_stock" ] } })

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