MongoDB quiz

Test your MongoDB knowledge with a free interactive quiz — 50 questions with answers and explanations. No signup needed to play.

If you insert a document without an `_id` field, what happens?

1. If you insert a document without an `_id` field, what happens?
2. In `db.users.find({}, {name: 1, _id: 0})`, what does the second argument do?
3. How are dates typically stored in MongoDB?
4. In MongoDB terminology, what does a "collection" correspond to in a relational database?
5. What is BSON?
6. Which update operator increments a numeric field?
7. What does the `upsert` option do in an update?
8. What does a single-field index on `email` enable?
9. Which logical operator combines conditions so that ALL must match?
10. When deciding between embedding a sub-document and referencing it by id, the most common starting heuristic is:
11. What is an `ObjectId` in MongoDB?
12. How would you query for documents where `status` is either `"active"` or `"pending"`?

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