Database Queries with Mongoose

Overview

Mongoose provides a powerful way to interact with MongoDB through queries. You can retrieve, update, and delete documents using simple methods.

Finding Documents

You can find documents in a collection using the find() method:

const User = require('./models/User'); // Assuming you have a User model

// Find all users
User.find()
  .then(users => {
    console.log('All Users:', users);
  })
  .catch(err => {
    console.error('Error fetching users:', err);
  });

Finding One Document

To find a single document, you can use the findOne() method:

// Find a user by email
User.findOne({ email: 'john@example.com' })
  .then(user => {
    console.log('Found User:', user);
  })
  .catch(err => {
    console.error('Error fetching user:', err);
  });

Updating Documents

You can update documents using the updateOne() or updateMany() methods:

// Update a user's age
User.updateOne({ email: 'john@example.com' }, { age: 31 })
  .then(result => {
    console.log('Update Result:', result);
  })
  .catch(err => {
    console.error('Error updating user:', err);
  });

Deleting Documents

To delete a document, you can use the deleteOne() or deleteMany() methods:

// Delete a user by email
User.deleteOne({ email: 'john@example.com' })
  .then(result => {
    console.log('Delete Result:', result);
  })
  .catch(err => {
    console.error('Error deleting user:', err);
  });

Querying with Conditions

You can also query documents with specific conditions:

// Find users older than 25
User.find({ age: { $gt: 25 } })
  .then(users => {
    console.log('Users older than 25:', users);
  })
  .catch(err => {
    console.error('Error fetching users:', err);
  });