show dbs                       # List databases
use mydb                       # Switch database
db                             # Current database
db.dropDatabase()              # Drop current database

show collections               # List collections
db.createCollection("users")   # Create collection
db.users.drop()                # Drop collection
db.users.renameCollection("people") # Rename collection

db.users.insertOne({name: "Alice", age: 30})
db.users.insertMany([{name: "Bob"}, {name: "Carol"}])
db.users.find()                        # Find all
db.users.find({age: {$gt: 25}})        # Query with filter
db.users.findOne({name: "Alice"})
db.users.updateOne({name: "Alice"}, {$set: {age: 31}})
db.users.updateMany({}, {$inc: {age: 1}})
db.users.replaceOne({name: "Bob"}, {name: "Bobby", age: 28})
db.users.deleteOne({name: "Carol"})
db.users.deleteMany({age: {$lt: 20}})

db.users.find({age: {$gte: 18}}, {name: 1, age: 1, _id: 0}) # Select fields
db.users.find().sort({age: -1})                              # Sort descending
db.users.find().limit(5)                                     # Limit results
db.users.find().skip(10)                                     # Skip results
db.users.countDocuments({})                                  # Count docs

db.users.createIndex({name: 1})              # Create index
db.users.createIndex({age: -1, name: 1})     # Compound index
db.users.getIndexes()                        # List indexes
db.users.dropIndex("name_1")                 # Drop index

db.users.aggregate([
  {$match: {age: {$gte: 18}}},
  {$group: {_id: "$age", count: {$sum: 1}}},
  {$sort: {count: -1}}
])
db.users.distinct("name")                    # Unique values

db.createUser({user: "admin", pwd: "pass", roles: ["userAdminAnyDatabase"]})
db.dropUser("admin")
db.changeUserPassword("admin", "newpass")
db.getUsers()
db.runCommand({connectionStatus: 1})

mongoimport --db mydb --collection users --file users.json
mongoexport --db mydb --collection users --out users.json

mongodump --db mydb --out ./backup
mongorestore --db mydb ./backup/mydb

db.stats()                                  # Database stats
db.users.stats()                            # Collection stats
db.serverStatus()                           # Server info