MongoDB

Aggregation Commands

The aggregation pipeline provides powerful data processing capabilities. Learn to transform, group, and analyze data.

5 commands

Pro Tips

Put $match stages early in the pipeline to reduce data processed.

Add { allowDiskUse: true } for aggregations that exceed memory limits.

$ db.orders.aggregate([{ $match: { status: "completed" } }, { $group: { _id: "$customerId", total: { $sum: "$amount" } } }])

Match and group with sum.

$ db.users.aggregate([{ $group: { _id: "$status", count: { $sum: 1 } } }])

Count documents per group.

$ db.orders.aggregate([{ $lookup: { from: "users", localField: "userId", foreignField: "_id", as: "user" } }])

Join with another collection.

$ db.orders.aggregate([{ $unwind: "$items" }, { $group: { _id: "$items.product", total: { $sum: "$items.qty" } } }])

Flatten array and aggregate.

$ db.users.aggregate([{ $project: { fullName: { $concat: ["$firstName", " ", "$lastName"] }, age: 1 } }])

Transform document structure.