Delete all documents in collection in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What command deletes all documents in a MongoDB collection?

Use db.collection.deleteMany({}) to delete all documents in the collection.

beginner

What does the empty filter {} mean in deleteMany({})?

It means "match all documents" so every document in the collection will be deleted.

intermediate

How is deleteMany({}) different from drop() in MongoDB?

deleteMany({}) removes all documents but keeps the collection. drop() deletes the entire collection and its indexes.

intermediate

What happens if you run db.collection.deleteOne({}) with an empty filter?

It deletes only one document that matches the empty filter, so effectively it deletes one random document.

beginner

Why should you be careful when using deleteMany({})?

Because it deletes all documents in the collection, which can cause data loss if done unintentionally.

Which MongoDB command deletes all documents in a collection but keeps the collection itself?

A db.collection.drop()

B db.collection.deleteMany({})

C db.collection.removeOne({})

D db.collection.clear()

deleteMany({}) deletes all documents but keeps the collection. drop() deletes the entire collection.

What does the filter {} mean when used in deleteMany({})?

A Delete all documents

B Delete no documents

C Delete documents with empty fields

D Delete documents with null values

An empty filter {} matches all documents, so all documents are deleted.

What is the effect of db.collection.deleteOne({})?

A Deletes no documents

B Deletes all documents

C Deletes the collection

D Deletes one document

deleteOne({}) deletes one document matching the filter, here the empty filter matches any document.

Which command removes the entire collection including its indexes?

A db.collection.deleteMany({})

B db.collection.deleteOne({})

C db.collection.drop()

D db.collection.removeAll()

drop() deletes the whole collection and its indexes.

Why should you be cautious when using deleteMany({})?

A It can delete all documents causing data loss

B It can delete the collection

C It does not delete any documents

D It can delete only one document

deleteMany({}) deletes all documents, which can cause data loss if used by mistake.

Explain how to delete all documents in a MongoDB collection without deleting the collection itself.

Think about the command that removes documents but not the collection.

Describe the difference between deleteMany({}) and drop() in MongoDB.

One removes data, the other removes the whole container.