The aggregation pipeline passes documents through stages, like an assembly line:
$match: filter (like WHERE).$group: group and calculate (like GROUP BY), with$sum,$avg,$max…$sort,$limit,$project,$lookup(join another collection).
MongoDB Aggregation Pipeline
Group, filter and transform data in stages.
✍️ 2 exercises in this lessonKey Takeaways: MongoDB Aggregation Pipeline
Mastering MongoDB Aggregation Pipeline helps you write clean and reliable MongoDB code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
MongoDB Aggregation Pipeline Code Example
MongoDBdb.students.aggregate([
{ $match: { marks: { $gte: 60 } } },
{ $group: { _id: "$city", students: { $sum: 1 }, avgMarks: { $avg: "$marks" } } },
{ $sort: { avgMarks: -1 } }
])Output
[
{ _id: 'Karachi', students: 1, avgMarks: 94 },
{ _id: 'Lahore', students: 1, avgMarks: 81 },
{ _id: 'Rawalpindi', students: 1, avgMarks: 72 }
]
Run this example on your own computer. The "Get Started" lesson shows how to set it up.
MongoDB Aggregation Pipeline Practice Exercises
Check what you learned in “MongoDB Aggregation Pipeline”.
/ 2 solved
Fill in the blank
The stage that filters documents (like WHERE).
db.orders.aggregate([ { : { status: "paid" } } ])
✓ Correct!
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Multiple choice
Which stage groups documents and calculates totals?
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