How to Combine Two Collections Into One Collection Using MongoDB
Today, we will use the $lookup aggregate stage, pipeline and $unwind operators, $project filter stage, and MongoDB Compass to combine two collections into one collection. Combine Two Collections Into One Collection Using MongoDB We have different approaches for combining two collections into one collection using MongoDB. Some of them are given below, which we will cover in this tutorial. Use the $lookup aggregate stage to join two collections Use the pipeline operator to join two collections based on the specified condition Use the $unwind operator to flat an array before attaching it to the resulted documents Use the $project filter stage in aggregation queries to join two collections Join two collections using a compass (a graphical interface of MongoDB) For all of the above scenarios, we must have a database containing two collections (same as tables in MySQL) populated with documents (same as records in MySQL).
