In this chapter, you learned about the MongoDB NumberDecimal class, based upon the BSON Decimal128 class, used to store financial numbers with high precision. You also learned that not all programming languages provide direct support for this class, which means a conversion might be necessary in order to perform processing.
Next, you learned how to handle database operations across collections. Several approaches were covered, including building block, embedded document, database reference, and DBRef approaches. You also learned how to produce a single iteration of documents across collections using the $lookup aggregation pipeline operator. After this, you learned about secondary updates and where they might be performed, as well as common pitfalls when working with documents across collections. These include problems associated with ensuring uniqueness, orphaned documents or fields, and keeping values synchronized.
Finally, at the end of this chapter, you learned about...
