Workshop mongo aggregations [musescodejs 16.11.19]

This document provides an overview and examples of using MongoDB aggregations. It begins with introductions to MongoDB basics like documents, collections, and simple queries. The bulk of the document focuses on the MongoDB aggregation pipeline, explaining what it is, common stages like $match, $group, $lookup, and examples of queries using those stages like filtering orders by postcode, grouping orders by type, joining products and brands with $lookup. It provides examples of more advanced techniques like lookups with sub-pipelines, grouping, dates, and exercises for readers to try themselves.