Unlock the power of complex MongoDB queries! This tutorial shows you exactly how to use the logical operators $and, $or, and $not to combine multiple conditions, plus the powerful $expr operator to compare fields within the same document.

What you will learn:

$and (Logical AND): How to find documents that match ALL specified conditions. (Note: This is often implied in simple queries, but $and is needed for certain structures).

$or (Logical OR): How to find documents that match AT LEAST ONE of the specified conditions.

$not (Logical NOT): How to find documents that DO NOT match a specific query.

$expr (Expression): The special operator that lets you compare two different fields against each other within the same document (e.g., find items where sold greater than in_stock).

Example ($or): db.users.find({ $or: [ { age: { $gt: 50 } }, { city: "New York" } ] })

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

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