Cheatsheets

wget -qO - https://www.mongodb.org/static/pgp/server-7.0.asc | sudo apt-key add -
echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu $(lsb_release -cs)/mongodb-org/7.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-7.0.list
sudo apt update && sudo apt install mongodb-org

show dbs                                 // List all databases
use database_name                        // Switch/create database
db                                       // Show current database
db.dropDatabase()                        // Delete current database
db.stats()                               // Database statistics

show collections                         // List collections
db.createCollection("users")             // Create collection
db.users.drop()                          // Delete collection
db.users.renameCollection("customers")   // Rename collection

db.users.insertOne({ name: "John", age: 30 })
db.users.insertMany([
  { name: "Alice", age: 25 },
  { name: "Bob", age: 35 }
])

db.users.find()                          // All documents
db.users.find().pretty()                 // Formatted output
db.users.find({ age: 30 })               // Exact match
db.users.find({ age: { $gt: 25 } })      // Greater than
db.users.findOne({ name: "John" })       // First match

db.users.updateOne(
  { name: "John" },
  { $set: { age: 31 } }
)
db.users.updateMany(
  { age: { $lt: 25 } },
  { $set: { status: "young" } }
)
db.users.replaceOne(
  { name: "John" },
  { name: "John Doe", age: 31 }
)

db.users.deleteOne({ name: "John" })
db.users.deleteMany({ age: { $lt: 25 } })
db.users.deleteMany({})                  // Delete all

$eq, $ne, $gt, $gte, $lt, $lte, $in, $nin
 
db.users.find({ age: { $gte: 25, $lte: 35 } })
db.users.find({ status: { $in: ["active", "pending"] } })

db.users.find({
  $and: [{ age: { $gte: 25 } }, { status: "active" }]
})
db.users.find({
  $or: [{ age: { $lt: 25 } }, { age: { $gt: 35 } }]
})

db.users.find({ email: { $exists: true } })
db.users.find({ age: { $type: "number" } })

$set, $unset, $inc, $mul, $rename, $min, $max
 
db.users.updateOne(
  { name: "John" },
  { $set: { age: 31 }, $inc: { score: 10 } }
)

$push, $pull, $addToSet, $pop
 
db.users.updateOne(
  { name: "John" },
  { $push: { tags: "mongodb" } }
)
db.users.updateOne(
  { name: "John" },
  { $addToSet: { tags: "database" } }
)

db.users.find({}, { name: 1, age: 1 })   // Include
db.users.find({}, { password: 0 })       // Exclude
db.users.find({}, { _id: 0, name: 1 })   // Exclude _id

db.users.find().sort({ age: -1 })        // Descending
db.users.find().limit(10)
db.users.find().skip(20).limit(10)       // Pagination
db.users.countDocuments()

db.users.createIndex({ email: 1 })       // Ascending
db.users.createIndex({ age: 1, name: 1 }) // Compound
db.users.createIndex({ email: 1 }, { unique: true })
db.users.createIndex({ description: "text" })
db.users.getIndexes()
db.users.dropIndex("email_1")

db.users.aggregate([
  { $match: { age: { $gte: 25 } } },
  { $group: { _id: "$status", count: { $sum: 1 } } },
  { $sort: { count: -1 } },
  { $limit: 10 }
])

// Count by field
db.users.aggregate([
  { $group: { _id: "$status", count: { $sum: 1 } } }
])
 
// Average
db.users.aggregate([
  { $group: { _id: null, avgAge: { $avg: "$age" } } }
])
 
// Unwind array
db.users.aggregate([
  { $unwind: "$tags" },
  { $group: { _id: "$tags", count: { $sum: 1 } } }
])
 
// Join collections
db.orders.aggregate([
  {
    $lookup: {
      from: "users",
      localField: "userId",
      foreignField: "_id",
      as: "user"
    }
  }
])

db.articles.createIndex({ content: "text" })
db.articles.find({ $text: { $search: "mongodb" } })
db.articles.find({ $text: { $search: "\"exact phrase\"" } })

db.createUser({
  user: "admin",
  pwd: "password",
  roles: ["readWrite", "dbAdmin"]
})
db.getUsers()
db.dropUser("username")

db.users.find({ age: 30 }).explain()
db.setProfilingLevel(2)
db.system.profile.find()

// Initialize a replica set
rs.initiate()
 
// Add members
rs.add("mongodb1.example.com:27017")
rs.add("mongodb2.example.com:27017")
rs.add({ host: "mongodb3.example.com:27017", priority: 0, hidden: true })
 
// View replica set status and config
rs.status()        // Current state, health, and roles
rs.conf()          // Full replica set configuration
 
// Step down primary (for maintenance)
rs.stepDown(120)   // Step down for 120 seconds
rs.stepDown()      // Step down with default timeout (60s)
 
// Other useful replica set commands
rs.isMaster()      // Check if current node is primary
rs.printReplicationInfo()  // View oplog details
rs.slaveOk()       // Allow reads from secondary (legacy)

// Connect to mongos (the sharding router)
// mongos --configdb configReplSet/config1:27019,config2:27019,config3:27019
 
// Enable sharding on a database
sh.enableSharding("mydb")
 
// Shard a collection
sh.shardCollection("mydb.users", { "_id": "hashed" })             // Hashed shard key
sh.shardCollection("mydb.orders", { "userId": 1, "date": 1 })     // Compound shard key
sh.shardCollection("mydb.logs", { "_id": 1 })                     // Ranged shard key
 
// Shard management
sh.status()                                // View sharding status
sh.addShard("shard1/mongodb1:27018")       // Add a shard
sh.removeShard("shard1")                   // Remove a shard
sh.startBalancer()                         // Re-enable balancer
sh.stopBalancer()                          // Pause balancer
sh.disableBalancing("mydb.users")          // Disable balancing for a collection
sh.enableBalancing("mydb.users")           // Enable balancing for a collection

// Zone-based sharding (tag-aware)
sh.addShardTag("shard1", "US-East")
sh.addShardTag("shard2", "EU-West")
sh.addTagRange("mydb.users", { country: "US" }, { country: "US" }, "US-East")

mongodump --db=mydb --out=/backup/         # Backup entire database
mongodump --uri="mongodb://user:pass@host:27017/mydb"  # Backup with connection string
mongodump --db=mydb --collection=users --out=/backup/  # Backup single collection
mongodump --db=mydb --gzip --archive=backup.gz         # Compressed archive backup
 
mongorestore --db=mydb /backup/mydb/                  # Restore database
mongorestore --drop --db=mydb /backup/mydb/           # Drop before restore
mongorestore --gzip --archive=backup.gz               # Restore from archive
mongorestore --uri="mongodb://user:pass@host:27017/mydb" /backup/mydb/

mongoexport --db=mydb --collection=users --out=users.json        # Export to JSON
mongoexport --db=mydb --collection=users --csv --out=users.csv   # Export to CSV
mongoexport --db=mydb --collection=users --query='{"age": {$gt: 25}}' --out=filtered.json
 
mongoimport --db=mydb --collection=users --file=users.json       # Import from JSON
mongoimport --db=mydb --collection=users --file=users.csv --type=csv --headerline
mongoimport --db=mydb --collection=users --file=users.json --drop # Drop before import
mongoimport --uri="mongodb://user:pass@host:27017/mydb" --collection=users --file=users.json

mongostat                          # Default output (1s interval)
mongostat 5                        # Every 5 seconds
mongostat --rowcount 10            # Stop after 10 rows
mongostat --uri="mongodb://user:pass@host:27017"  # Remote host
mongostat --discover               # Auto-discover replica set members
 
mongotop                           # Show read/write activity per collection
mongotop 5                         # Every 5 seconds
mongotop --locks                   # Include lock info
mongotop --uri="mongodb://user:pass@host:27017"