MongoDB Query & Aggregation Pipeline Cheat Sheet

Essential MongoDB syntax reference for developers. Covers CRUD operations, query filters, projection, indexing, and aggregation pipelines.

Read & Filter Operations

Find all documents in collectiondb.collection.find()

Filter documents by exact field valuedb.collection.find({ status: "active" })

Filter with comparison operators ($gte, $lte, $ne, $in)db.collection.find({ age: { $gte: 18, $lte: 65 } })

Filter array field matching all specified elementsdb.collection.find({ tags: { $all: ["react", "node"] } })

Projection: include name and email, exclude _iddb.collection.find({}, { name: 1, email: 1, _id: 0 })

Sort descending (-1) or ascending (1) with pagination limitdb.collection.find().sort({ createdAt: -1 }).limit(10)

Create & Update Operations

Insert single JSON document into collectiondb.collection.insertOne({ ... })

Insert batch array of documentsdb.collection.insertMany([{ ... }, { ... }])

Update specific field without overwriting documentdb.collection.updateOne({ _id }, { $set: { status: "verified" } })

Atomically increment numerical field on matching recordsdb.collection.updateMany({}, { $inc: { views: 1 } })

Update document if found, or insert if does not existdb.collection.updateOne({ email }, { $set: { lastLogin: new Date() } }, { upsert: true })

Aggregation Pipeline

Filter stream documents before grouping or projection$match: { status: "paid" }

Group documents and calculate aggregate sums, averages, or counts$group: { _id: "$userId", total: { $sum: "$amount" } }

Sort grouped stream results$sort: { total: -1 }

Perform left outer join with another collection$lookup: { from: "users", localField: "userId", foreignField: "_id", as: "user" }

Deconstruct array field into separate document for each element$unwind: "$tags"

Frequently Asked Questions

• What is the performance difference between $set and replacing a document in MongoDB?

`$set` only modifies the specified fields in place without transferring the entire document over the network or touching unmodified fields, dramatically reducing network IO and write locks.