Aggregation operations process data records and return computed results. Aggregation operations group values from multiple documents together and can perform a variety of operations on the grouped data to return a single result.
MongoDB provides three ways to perform aggregation:
- Aggregation pipeline
- Map-reduce function
- Single-purpose aggregation methods
db.orders.aggregate([
{ $match: { status: "A" } },
{ $group: { _id: "$cust_id", total: { $sum: "$amount" } } }
])
