// Switch to database test1

use test1;

// List all users

db.users.find();

// Find the users whose first names are John

db.users.find(
    {
        firstName: 'John'
    }
);

// Find the first names of the users whose last names are Doe

db.users.find(
    {
        lastName: 'Doe'
    },
    {
        firstName: true
    }
);

// Find the users who are older than 20

db.users.find(
    {
        age: { $gt: 20 }
    }
);

// Find the users who are older than 20 and younger than 30

db.users.find(
    {
        age: { $gt: 20, $lt: 30 }
    }
);

// Find the users who are younger than 20 or older than 30

db.users.find(
    {
        $or: [ {age: {$lt: 20}}, {age: {$gt: 30}} ]
    }
);

// Find the users who in CA

db.users.find(
    {
        'address.state' : 'CA'
    }
);