db.persons.aggregate([]).length([1]);

db.persons.aggregate([{

$group: { _id: "$customer.gender" } },{ $count: "genderCount"}]);

db.persons.aggregate([

{ $group: { _id: "$customer.gender", count: { $sum: 1 } } }]);

db.persons.aggregate([]).size();

db.persons.aggregate([{$count:"total"}]);

db.persons.aggregate([]).itcount();

db.persons.aggregate([]).toArray().length;

Using the db.collection.removeAll() method.

Using the db.collection.deleteMany({}) method.

Using the db.collection.remove({}) method.

Using the db.collection.deleteAll() method.

 One

document for the population of each zip code, sorted in descending order

One

document for the population of each zip code, sorted in ascending order

One

document for the population of each zip code, sorted in random order

10

documents for the population of each zip code