mongoDB notes | asboyer.com

Basics

show dbs

shows databases

use appdb

switch to appdb

show collections

collections are like tables in sql, where you store your data

db.dropDatabase()

still can be in deleted database

db.users.insertOne({name: "John"})

db.users.find()

id is generated everytime you add something

no need to define schema - this is a nosql database

every object you store is called a document

add anything you inside a collection

appdb> db.users.find()
[
  { _id: ObjectId('66c7534c346e817e36607e64'), name: 'John' },
  {
    _id: ObjectId('66c753cc346e817e36607e65'),
    name: 'Sally',
    age: 19,
    address: { street: '987 N St.' },
    hobbies: [ 'Running' ]
  }
]

db.users.insertMany([{}, {}])

insert an array of objects

Querying

db.users.find().limit(2)

db.users.find.sort({name: 1}).limit(2) //could be -1 to go opposite order

db.users.find.sort({age: -1, name: 1}).limit(2) //could be -1 to go opposite order

db.users.find.find().skip(1).limit(2) 

// skips the first one

db.users.find({name: "Kyle"})
db.users.find({age: 26})

db.users.find({name: "Kyle"}, {name: 1, age: 26, _id: 0})

// complex query
db.users.find({ name: { $eq: "Sally" }}) // equal
db.users.find({ name: { $ne: "Sally" }}) // not equal

// $gt: greater than
// $gte: greater than or equal to
// $lte: less than or equal to
// $in: pass in array of items and check if its in the list
// $nin: opposite of nin

db.users.find({ age: { $exists: true }}) // return users that have an age field
// will return even if field is "null"

db.users.find({ age: { $gte: 20, $lte: 40 }}) // 20 < x < 40
db.users.find({ age: { $gte: 20, $lte: 40 }, name: "Kyle" }) // 20 < x < 40 and named kyle

db.users.find({ $and: [{age: 26}, {name: "Kyle"}]}) // dont need to use $and very much
db.users.find({ $or: [{age: {$lte: 20}}, {name: "Kyle"}]}) // return less than 20 or someone named kyle

db.users.find({age: {$not: {$lte: 20}}}) // all of users that are not less than or equal to 20

db.users.find({$expr: {$gt: ["$debt", "$balance"]}}) // $expr: expression
// checking if the debt is greater than the balance

db.users.find({ "address.street": "123 Main St"}) // check objects within objects

db.users.findOne() // just find one object that matches the query

Updating

db.users.updateOne({age: 26}, {$set: {age: 27}})
//                   find          update

db.users.updateOne({_id: ObjectId('66c7534c346e817e36607e64')}, {$set: {name: "new name"}})

// can use $inc instead of $set to increment a number

// can use $rename to rename a property.
db.users.updateOne({_id: ObjectId('66c7534c346e817e36607e64')}, {$rename: {name: "firstName"}})
// this renames the "name" tag to firstName

db.users.updateOne({_id: ObjectId('66c7534c346e817e36607e64')}, {$unset: {age: ""}})
// $unset completely removes the age property

// $push adds to an array
db.users.updateOne({_id: ObjectId('66c7534c346e817e36607e64')}, {$push: {hobbies: "bowling"}})

// $pull removes from an array
db.users.updateOne({_id: ObjectId('66c7534c346e817e36607e64')}, {$pull: {hobbies: "bowling"}})

//update many users
db.users.updateMany({ address: {$exists: true}}, {$unset: {address: ""}})
//  remove address from all users that have an address

db.users.replaceOne({ age: 30}, {name: "John"})
// find at that location, then replaces it completely with the object
// use update instead of replace

db.users.deleteOne({})
// takes in the same params as find

db.users.deleteMany({})
// takes in same paramss as find