Aggregation operations are very important in any type of database whether it is SQL or NoSQL. To perform aggregations operations, MongoDB group values from multiple documents together and then perform a variety of operations on grouped data to return a single result. SQL uses aggregate functions to return a single value calculated from values in columns.
MongoDB has three ways to perform aggregation: the aggregation pipeline, the map-reduce function, and the single purpose aggregation methods.
In this article, we will focus on aggregation pipeline. I’ll try to cover each major section of it using simple examples. We will be writing mongo shell commands to perform aggregation. Continue reading “Aggregation in MongoDB”