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Learn MongoDB 4.x

You're reading from   Learn MongoDB 4.x A guide to understanding MongoDB development and administration for NoSQL developers

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Product type Paperback
Published in Sep 2020
Publisher Packt
ISBN-13 9781789619386
Length 610 pages
Edition 1st Edition
Tools
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Author (1):
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Doug Bierer Doug Bierer
Author Profile Icon Doug Bierer
Doug Bierer
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Table of Contents (22) Chapters Close

Preface 1. Section 1: Essentials
2. Introducing MongoDB 4.x FREE CHAPTER 3. Setting Up MongoDB 4.x 4. Essential MongoDB Administration Techniques 5. Section 2: Building a Database-Driven Web Application
6. Fundamentals of Database Design 7. Mission-Critical MongoDB Database Tasks 8. Using AJAX and REST to Build a Database-Driven Website 9. Section 3: Digging Deeper
10. Advanced MongoDB Database Design 11. Using Documents with Embedded Lists and Objects 12. Handling Complex Queries in MongoDB 13. Section 4: Replication, Sharding, and Security in a Financial Environment
14. Working with Complex Documents Across Collections 15. Administering MongoDB Security 16. Developing in a Secured Environment 17. Deploying a Replica Set 18. Replica Set Runtime Management and Development 19. Deploying a Sharded Cluster 20. Sharded Cluster Management and Development 21. Other Books You May Enjoy

Building queries involving embedded arrays

Management is concerned about customer complaints regarding cleanliness. You have been instructed to produce a report on properties where more than 50% of the reviews for that property report a low cleanliness score (for example, 3 or less).

When conducting queries of any type, it's important to be aware of the database document structure. In this case, we need to examine the properties collection. Using MongoDB Compass, all you need to do is to connect to the database and select the booksomeplace database, as well as the properties collection. In the list view, you can click on the reviews field to get an idea of the structure, as shown here:

As you can see, reviews are represented as embedded arrays. Following the logic presented in the earlier sub-section in this chapter, your first thought might be to construct a query document such as this: {"reviews.cleanliness":{$lt:3}}:

This is not exactly the information we are...

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