MongoDB Cheat Sheet

CRUD Operations

insertOne()Insert document
insertMany()Insert multiple
find()Query documents
findOne()Query single
updateOne()Update first match
updateMany()Update all matches
deleteOne()Delete first match
deleteMany()Delete all matches

Query Operators

$eq, $neEqual, not equal
$gt, $gteGreater than
$lt, $lteLess than
$in, $ninIn array
$and, $orLogical operators
$existsField exists
$regexPattern match

Update Operators

$setSet field value
$unsetRemove field
$incIncrement value
$pushAdd to array
$pullRemove from array
$addToSetAdd unique
$renameRename field

Database Commands

show dbsList databases
use dbnameSwitch database
show collectionsList collections
db.dropDatabase()Drop database
db.stats()DB statistics

Query Examples

// Find all documents
db.users.find({})

// Find with conditions
db.users.find({ age: { $gte: 18 } })

// Multiple conditions (AND)
db.users.find({
  status: "active",
  age: { $gte: 21 }
})

// OR condition
db.users.find({
  $or: [
    { status: "active" },
    { role: "admin" }
  ]
})

// Projection (select fields)
db.users.find({}, { name: 1, email: 1, _id: 0 })
          

Aggregation Pipeline

db.orders.aggregate([
  // Match stage (filter)
  { $match: { status: "completed" } },

  // Group stage
  { $group: {
    _id: "$customerId",
    totalAmount: { $sum: "$amount" },
    orderCount: { $sum: 1 }
  }},

  // Sort stage
  { $sort: { totalAmount: -1 } },

  // Limit results
  { $limit: 10 }
])
          

Aggregation Stages

$matchFilter docs
$groupGroup by field
$sortSort results
$projectReshape docs
$lookupJoin collections
$unwindFlatten arrays

Indexes

// Create index
db.users.createIndex({ email: 1 })

// Unique index
db.users.createIndex(
  { email: 1 },
  { unique: true }
)

// Compound index
db.users.createIndex({
  status: 1,
  createdAt: -1
})

// List indexes
db.users.getIndexes()
          

Update Examples

// Update single document
db.users.updateOne(
  { _id: ObjectId("...") },
  { $set: { name: "New Name" } }
)

// Update multiple documents
db.users.updateMany(
  { status: "inactive" },
  { $set: { archived: true } }
)

// Upsert (insert if not exists)
db.users.updateOne(
  { email: "user@example.com" },
  { $set: { lastLogin: new Date() } },
  { upsert: true }
)

// Increment value
db.posts.updateOne(
  { _id: postId },
  { $inc: { views: 1 } }
)
          

Array Operators

$elemMatchMatch element
$allContains all
$sizeArray length
$sliceArray subset
$First match

Cursors

.sort()Sort results
.limit()Limit count
.skip()Skip documents
.count()Count results
.explain()Query analysis

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