MongoDB Shell Basics

mongodb-shell-basics.txt

// List all databases
show dbs

// Switch to a database
use dbname

// List all collections in the current database
show collections

// Drop current database
db.dropDatabase()

// Create collection
db.createCollection("students")

// Create collection (with advanced options)
db.createCollection("teachers", {
    capped: true,         // set capped mode to true
    size: 1000000,        // limit data size to 1000000 bytes
    max:100               // limit number of documents to 100
}, {
    autoIndexId: false    // disable indexes for _id (not recommended)
})

// Drop collection
db.students.drop()


// Get all documents in a collection
db.students.find()

// Insert a single document in a collection
db.students.insertOne({name: "Spongebob", age: 30, gpa: 3.2})

// Insert multiple documents at once in a collection
db.students.insertMany([
  {name: "Patrick", age: 38, gpa: 1.5}, 
  {name: "Sandy", age: 27, gpa: 4.0}, 
  {name: "Gary", age: 18, gpa: 2.5}
])

// Insert document with variety of data types
db.students.insertOne({
... name: "Larry",    // string
... age: 32,          // integer
... gpa: 2.8,         // double
... fullTime: false,  // boolean
... registeredDate: new Date("2025-08-22T11:25:32"),    // date
... graduationDate: null,                               // null
... courses: ["Biology", "Chemistry", "Calculus"],      // array
... address: {                                          // nested document
... street: "123 Fake St.",
... city: "Bikini Bottom",
... zip: 12345
... }
... })


// Sort documents by a particular field ("name" in this case) in ascending order (the value "1")
db.students.find().sort({name: 1})

// Sort documents by a particular field ("name" in this case) in descending order (the value "-1")
db.students.find().sort({name: -1}

// Limit the numbeer of documents returned in a query (in this case just 3 document)
db.students.find().limit(3)

// Combine sort and limit
db.students.find().sort({gpa: -1}).limit(1)

// Filter documents if field is equal to a value (name == "Spongebob")
db.students.find({name: "Spongebob"})

// Filter with multiple fields
db.students.find({gpa: 4.0, fullTime: true})

// Select only a few fields (in this case, a "name") to return with "projection"
db.students.find({}, {name: true})

// Forcefully omit id field from a query 
db.students.find({}, {_id:false, name: true})

// Update a field in a document
db.students.updateOne({ name: "Spongebob" }, { $set: {fullTime: true} })

// Update a field in a document (using ID)
db.students.updateOne({_id: ObjectId('68a7dd81785f6134dc89b03d')}, { $set: {fullTime: false} })

// Remove/unset a field in a document (using ID)
db.students.updateOne({_id: ObjectId('68a7dd81785f6134dc89b03d')}, {$unset: {fullTime:""}})

// Update multiple documents at once
db.students.updateMany({}, {$set: {fullTime: false} })

// Update only those documents if a particular field doesn't exists
db.students.updateMany({fullTime:{$exists: false}}, {$set: {fullTime: true}})

// Delete a document that matched a filter (in this case name == "Larry")
db.students.deleteOne({name: "Larry"})

// Delete multiple documents
db.students.deleteMany({fullTime: false})

// Delete multiple documents that have a missing field (in this case "registerDate")
db.students.deleteMany({registerDate: {$exists:false}})


// Comparison operators
// Example: db.students.find({age: {$gt: 25})    // age > 25
{ field: value }                       // field == value
{ field: { $eq: value } }              // field == value
{ field: { $ne: value } }              // field !== value
{ field: { $lt: value } }              // field < value
{ field: { $lte: value } }             // field <= value
{ field: { $gt: value } }              // field > value
{ field: { $gte: value } }             // field >= value
{ field: { $gte: 3, $lte: 4 } }        // field >= 3 && field <= 4
{ field: { $in: ["a", "b", "c"] } }    // field in ["a", "b", "c"]
{ field: { $nin: ["a", "b", "c"] } }   // field not in ["a", "b", "c"]

// Logical operators
{ $and: [{a:4}, {b:5}, {c:6}] }       // a==4 && b==5 && c==6
{ $or: [{a:4}, {b:5}, {c:6}] }        // a==4 || b==5 || c==6
{ $nor: [{a:4}, {b:5}, {c:6}] }       // !(a==4 || b==5 || c==6)
{ field: { $not: {$gte: 4} } }        // !(field > 4)

// Indexes
db.student.getIndexes()               // show all indexes
db.student.createIndex({name: 1})     // add index to 'name' with ASC order
db.student.dropIndex("name_1")        // drop an index