What does $not do?
$not is a logical negation operator. It inverts a condition, making it the opposite.
Example:
js
db.users.find({
age: { $not: { $gt: 18 } }
})The query returns documents where age is not greater than 18 (that is, 18 or less).
The key idea: $not is applied on top of another operator ($gt, $lt, $regex, etc.) and flips its condition.
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