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Lesson 1113 min read

Inserting Documents

Add new documents to a collection using insertOne and insertMany.

insertOne

insertOne() adds a single document to a collection.

db.users.insertOne({
  name: "Ada Lovelace",
  email: "ada@example.com",
  age: 28,
});
Shell Result

Click Run to see what this code prints.

insertMany

insertMany() adds multiple documents in a single operation, more efficient than calling insertOne() repeatedly.

db.users.insertMany([
  { name: "Grace Hopper", age: 34 },
  { name: "Alan Turing", age: 29 },
  { name: "Katherine Johnson", age: 41 },
]);
Ordered by Default

By default, insertMany() stops at the first error, leaving earlier documents inserted. Pass { ordered: false } to continue inserting the remaining documents even if one fails.

Understanding the Result

Both operations return an object confirming success and listing the auto-generated _id value(s) — useful for immediately referencing the newly created document elsewhere in your application logic.

Common Beginner Mistakes

Assuming insertMany() is always atomic across all documents

By default (ordered: true), a failure partway through still leaves earlier documents inserted — it isn't all-or-nothing unless wrapped in a transaction.

Manually generating an _id that might collide

Let MongoDB generate the ObjectId automatically unless you have a specific, well-understood reason to supply your own.

FAQs

Practically yes, bound by the 48MB maximum BSON message size — for very large bulk inserts, batch them into smaller chunks.

Nothing special — that field simply doesn't exist on this document; querying for it will treat it as undefined/absent, not an error.

Summary

insertOne and insertMany cover single and bulk document creation, both returning the generated _id values. Next, you'll learn to read data back out with find().

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Finding Documents