Commonly used stages in an aggregation pipeline:
• $match: filters incoming documents (similar to find())
• $group: groups documents by a specified key and computes totals ($sum), averages ($avg), and so on.
javascript
db.orders.aggregate([
// Stage 1: Filter documents with status "A"
{ $match: { status: "A" } },
// Stage 2: Group by customer_id and calculate total amount
{ $group: { _id: "$cust_id", total: { $sum: "$amount" } } }
])You should see
(This will group orders with status "A" by each customer and calculate the total amount)