MEAN MongoDB Advanced Operations 2

Question 1

What is the MongoDB $unwind aggregation stage used for?

Accepted Answer

Deconstructs an array field into separate documents

Answer

$unwind deconstructs an array field, outputting one document per array element with the field replaced by that element's value.

Question 2

Which MongoDB feature allows you to enforce a schema on a collection?

Accepted Answer

Schema Validation with $jsonSchema

Answer

MongoDB's built-in schema validation using $jsonSchema lets you define required fields, types, and constraints that documents must satisfy.

Question 3

What does the MongoDB `upsert` option do in an update operation?

Accepted Answer

Inserts a new document if no matching document exists

Answer

When upsert: true is set, MongoDB inserts a new document if no document matches the filter criteria, otherwise it updates the existing one.

Question 4

In MongoDB, what is a capped collection?

Accepted Answer

A fixed-size collection that overwrites oldest documents when full

Answer

Capped collections have a fixed size and automatically overwrite the oldest entries in insertion order when the size limit is reached.

Question 5

Which operator is used to atomically increment a numeric field in a MongoDB document?

Accepted Answer

$inc

Answer

The $inc operator atomically increments (or decrements with a negative value) a numeric field by the specified amount in a single operation.

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