MongoDB Insert Documents

To add data to MongoDB, you insert documents into a collection with insertOne() or insertMany().

insertOne()

Example

javascript

use institute

db.students.insertOne({
  name: "Ali Khan",
  city: "Karachi",
  age: 19,
  marks: 78,
  course: "Web Development",
  skills: ["HTML", "CSS"]
})

Output

{
  acknowledged: true,
  insertedId: ObjectId('6710a1f2c3b4d5e6f7a8b901')
}

acknowledged: true means the server saved it
insertedId is the _id MongoDB created for the new document

insertMany()

Pass an array of documents to insert several at once:

Example

javascript

db.students.insertMany([
  { name: "Ayesha Siddiqui", city: "Lahore", age: 21, marks: 85,
    course: "Python Programming", skills: ["Python"] },
  { name: "Bilal Ahmed", city: "Karachi", age: 22, marks: 64,
    course: "Web Development", skills: ["HTML", "JavaScript"] },
  { name: "Fatima Noor", city: "Islamabad", age: 20, marks: 92,
    course: "Graphic Designing", skills: ["Photoshop", "Illustrator"] },
  { name: "Hamza Raza", city: "Karachi", age: 18, marks: 70 },
  { name: "Sana Iqbal", city: "Lahore", age: 23, marks: 88,
    course: "Python Programming", skills: ["Python", "SQL"] }
])

Output

{
  acknowledged: true,
  insertedIds: {
    '0': ObjectId('6710a1f2c3b4d5e6f7a8b902'),
    '1': ObjectId('6710a1f2c3b4d5e6f7a8b903'),
    '2': ObjectId('6710a1f2c3b4d5e6f7a8b904'),
    '3': ObjectId('6710a1f2c3b4d5e6f7a8b905'),
    '4': ObjectId('6710a1f2c3b4d5e6f7a8b906')
  }
}

The collection now has the six students used in the rest of this tutorial. Your ObjectId values will be different.

If you followed the last lesson, first remove the test document with db.students.deleteOne({ name: "Test Student" }), so your results match the examples.

The _id Field

Every document must have a unique _id.

If you leave it out, MongoDB adds an ObjectId, a 12-byte value that includes the time it was created
You may set your own _id, such as a roll number, as long as it is unique

Example

javascript

db.courses.insertOne({ _id: "WEB", title: "Web Development", months: 6 })

Output

{ acknowledged: true, insertedId: 'WEB' }

Inserting another document with _id: "WEB" fails:

Output

MongoServerError: E11000 duplicate key error collection: institute.courses index: _id_ dup key: { _id: "WEB" }

Value Types

Type	Example
String	`"Karachi"`
Number	`19`, `78.5`
Boolean	`true`, `false`
Array	`["HTML", "CSS"]`
Embedded document	`{ phone: "0300-1112233" }`
Date	`new Date("2026-10-15")`
Null	`null`
ObjectId	`ObjectId('6710a1f2c3b4d5e6f7a8b901')`
Decimal	`NumberDecimal("2450.50")` for exact money values

Nested Data and Dates

A course document can hold its own list of modules, each one a small document:

Example

javascript

db.courses.insertOne({
  _id: "PY",
  title: "Python Programming",
  months: 4,
  startDate: new Date("2026-11-02"),
  modules: [
    { week: 1, topic: "Variables and types" },
    { week: 2, topic: "Loops and functions" }
  ]
})

Output

{ acknowledged: true, insertedId: 'PY' }

This is called embedding. Data that is always read together lives in one document, so no join is needed.

Ordered and Unordered Inserts

By default, insertMany stops at the first error. Add { ordered: false } to insert every valid document and report the failed ones at the end:

Example

javascript

db.courses.insertMany(
  [ { _id: "GD", title: "Graphic Designing" }, { _id: "WEB", title: "Duplicate" } ],
  { ordered: false }
)

Here GD is saved, and only the duplicate WEB fails.

Exercise

What happens if you insert a document without an _id field?

The insert failsThe document is saved without any _idMongoDB adds a unique ObjectId as the _idMongoDB uses the name field as the _id