4. CRUD Operations in Mongoose

Create

With pg, you insert data by running SQL commands:

pool.query(
  `INSERT INTO students (first_name, last_name, email, enrollment_date) VALUES ($1, $2, $3, $4)`,
  ['Alice', 'Johnson', 'alice.johnson@example.com', '2024-09-15']
);

In Mongoose, you create and save an instance of a model:

const newStudent = new Student({
  firstName: 'Alice',
  lastName: 'Johnson',
  email: 'alice.johnson@example.com',
  enrollmentDate: '2024-09-15',
});

newStudent.save()
  .then(student => console.log('Saved:', student))
  .catch(err => console.error('Error:', err));

Read

• With pg:

  pool.query(
    `SELECT * FROM students WHERE email = $1`,
    ['alice.johnson@example.com']
  );

• With Mongoose:

  Student.findOne({ email: 'alice.johnson@example.com' })
    .then(student => console.log('Found:', student))
    .catch(err => console.error('Error:', err));

Update

• With pg:

  pool.query(
    `UPDATE students SET email = $1 WHERE first_name = $2 AND last_name = $3`,
    ['alice.newemail@example.com', 'Alice', 'Johnson']
  );

• With Mongoose:

  Student.updateOne(
    { firstName: 'Alice', lastName: 'Johnson' },
    { email: 'alice.newemail@example.com' }
  )
  .then(res => console.log('Updated:', res))
  .catch(err => console.error('Error:', err));

Delete

• With pg:

  pool.query(
    `DELETE FROM students WHERE email = $1`,
    ['alice.johnson@example.com']
  );

• With Mongoose:

  Student.deleteOne({ email: 'alice.johnson@example.com' })
    .then(res => console.log('Deleted:', res))
    .catch(err => console.error('Error:', err));