Basic MongoDB Queries

All the queries in this section are top-level queries; that is, they are based on the top-level (also known as root-level) fields in the documents. We will learn about the basic query operators by writing queries against the root fields.

Finding Documents

The most basic query in MongoDB is performed with the find() function on the collection. When this function is executed without any argument, it returns all the documents in a collection. For example, consider the following query:

db.comments.find()

This query calls the find() function on the collection named comments. When executed on a mongo shell, it will return all the documents from the collection. To return only specific documents, a condition can be provided to the find() function. When this is done, the find() function evaluates it against each and every document in the collection and returns the documents that match the condition.

For example, consider that instead of retrieving all the...