Basic CRUD with the Driver

Objectives

By the end of this lesson, you should be able to:

• Insert one or many documents into a collection
• Query documents with find, findOne, and a filter object
• Update and delete documents with the native driver

💡 Why this matters: This is MongoDB’s version of Modules 1 and 2, the CRUD basics everything else in the MongoDB half of this course builds on.

⚠️ A note on verification: as in the last lesson, this course’s own tooling has no route to a local MongoDB server. The code and output below reflect the official mongodb driver’s stable, current, documented API. Try it yourself, on your own machine, against a real MongoDB server.

Inserting Documents

const db = client.db('school');
const students = db.collection('students');

const result = await students.insertOne({ name: 'Erin', grade: 9 });
console.log(result);

{
  acknowledged: true,
  insertedId: ObjectId('65f1a2b3c4d5e6f7a8b9c0d1')
}

insertOne returns an insertedId, MongoDB generates a unique ObjectId automatically, the equivalent of SERIAL’s auto-incrementing id in PostgreSQL, except it’s a longer, globally unique value rather than a simple counter.

Inserting several documents at once:

const result = await students.insertMany([
  { name: 'Jordan', grade: 10 },
  { name: 'Maya', grade: 9 }
]);
console.log(result.insertedCount);

2

Reading Documents

find returns every matching document, as a cursor, not an array directly:

const cursor = students.find({});
const all = await cursor.toArray();
console.log(all);

[
  { _id: ObjectId('...'), name: 'Erin', grade: 9 },
  { _id: ObjectId('...'), name: 'Jordan', grade: 10 },
  { _id: ObjectId('...'), name: 'Maya', grade: 9 }
]

{} as the filter matches every document, toArray() pulls the full result set into a normal array. Filtering works with a plain object, matched field by field:

const ninthGraders = await students.find({ grade: 9 }).toArray();
console.log(ninthGraders);

[
  { _id: ObjectId('...'), name: 'Erin', grade: 9 },
  { _id: ObjectId('...'), name: 'Maya', grade: 9 }
]

findOne returns a single matching document directly (not a cursor), or null if nothing matches:

const jordan = await students.findOne({ name: 'Jordan' });
console.log(jordan);

{ _id: ObjectId('...'), name: 'Jordan', grade: 10 }

Updating Documents

const result = await students.updateOne(
  { name: 'Erin' },
  { $set: { grade: 10 } }
);
console.log(result);

{
  acknowledged: true,
  matchedCount: 1,
  modifiedCount: 1
}

The first argument is the filter (which document to update), the second describes the change, $set updates specific fields without touching the rest of the document. Unlike SQL’s UPDATE, MongoDB doesn’t overwrite the whole document by default, $set is what makes it a partial update.

updateMany applies the same change to every matching document:

const result = await students.updateMany(
  { grade: 9 },
  { $set: { status: 'active' } }
);
console.log(result.modifiedCount);

1

Deleting Documents

const result = await students.deleteOne({ name: 'Jordan' });
console.log(result);

{ acknowledged: true, deletedCount: 1 }

deleteMany removes every matching document, exactly like deleteOne but not stopping after the first match.

Try It

1. Insert three documents into a students collection using insertOne and insertMany.
2. Query all of them with find({}).toArray(), and a filtered subset with find({ grade: 9 }).toArray().
3. Update one document’s field with updateOne and $set, and confirm modifiedCount is 1.
4. Delete one document with deleteOne, then confirm it’s gone with another find.

Recap

• insertOne/insertMany add documents, each gets an auto-generated _id unless one is provided.
• find returns a cursor (call .toArray() for a plain array), findOne returns a single document or null.
• updateOne/updateMany take a filter and a $set (or other update operator), deleteOne/deleteMany take a filter alone.

This is the final lesson of this module before exercises. Next module: Mongoose, schemas and validation on top of everything covered here.