Introduction to MongoDB Aggregation

This section contains key definitions for this lesson, as well as the code for an aggregation pipeline.

Definitions

• Aggregation: Collection and summary of data

• Stage: One of the built-in methods that can be completed on the data, but does not permanently alter it

• Aggregation pipeline: A series of stages completed on the data in order

Structure of an Aggregation Pipeline

db.collection.aggregate([
    {
        $stage1: {
            { expression1 },
            { expression2 }...
        },
        $stage2: {
            { expression1 }...
        }
    }
])