Book Image

Learn MongoDB 4.x

By : Doug Bierer
Book Image

Learn MongoDB 4.x

By: Doug Bierer

Overview of this book

When it comes to managing a high volume of unstructured and non-relational datasets, MongoDB is the defacto database management system (DBMS) for DBAs and data architects. This updated book includes the latest release and covers every feature in MongoDB 4.x, while helping you get hands-on with building a MongoDB database app. You’ll get to grips with MongoDB 4.x concepts such as indexes, database design, data modeling, authentication, and aggregation. As you progress, you’ll cover tasks such as performing routine operations when developing a dynamic database-driven website. Using examples, you’ll learn how to work with queries and regular database operations. The book will not only guide you through design and implementation, but also help you monitor operations to achieve optimal performance and secure your MongoDB database systems. You’ll also be introduced to advanced techniques such as aggregation, map-reduce, complex queries, and generating ad hoc financial reports on the fly. Later, the book shows you how to work with multiple collections as well as embedded arrays and documents, before finally exploring key topics such as replication, sharding, and security using practical examples. By the end of this book, you’ll be well-versed with MongoDB 4.x and be able to perform development and administrative tasks associated with this NoSQL database.
Table of Contents (22 chapters)
Section 1: Essentials
Section 2: Building a Database-Driven Web Application
Section 3: Digging Deeper
Section 4: Replication, Sharding, and Security in a Financial Environment
Working with Complex Documents Across Collections

Applying projections to your query

The second argument to the db.collection.find() and db.collection.findOne() commands, also using JSON syntax, is the projection argument. The projection argument allows you to control which fields appear or do not appear in the final output. 

Here is a summary of the projection options:

Projection expression What appears in the output
{ }  (or blank) All fields
{ "field1" : 1 } Only field1 and the _id fields
{ "field1" : 0 } All fields except for field1
{ "field1" : 1, "_id" : 0 } Only field1
{ "field1" : 1, "field2" : 0 } Not allowed!  Cannot have a mixture of include and exclude (except for the _id field)

For this example, we will assume that the management has asked for the name and email address of all customers from Quebec. Accordingly, you construct a query that uses the projection argument to only include fields pertinent to the name and address...