In an inclusion approach projection, what is the default value for a field?

In an inclusion approach projection in MongoDB, the default value for fields is indeed set to 0, unless the field is explicitly the _id field, which is included by default. This means that if you only specify certain fields to be included in the results, all other fields will be excluded unless you indicate otherwise.

The inclusion approach is often applied when querying documents, allowing you to retrieve only the necessary data. By explicitly excluding fields you do not need (by setting them to 0), the results become more streamlined and efficient.

This behavior makes it clear why the default value is important; if no other fields are specified, all fields except for _id will be excluded from the output, ensuring that only the relevant data is retrieved. This feature is particularly useful in scenarios where documents contain large amounts of data, and you want to optimize performance by minimizing the amount of data transferred and processed.

Understanding this default behavior is fundamental for MongoDB users, as it shapes the way data is accessed and manipulated within the database architecture.