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db.students.find({Hobbies: {$all: ["Walking" ,"Reading"]}})

db.students.find({experience:{$size:3}})

db.students.find({"experience.company":"Amazon"})

db.students.find({"experience.company":"Spotify"}).size()

Update Nested Array!

(Q) For all experiences lesser than and equal to 1 year for all students, add a new field : neglect:true

{

name: 'Pradyumna'
hobbies: ['Singing', 'Cricket']
bio: 'I am a coder'
experience: [
    {company: "TCS", duration: 1 },
    {company: "TCS", duration: 2 },
    {company: "TCS", duration: 1 }
],

age : 15 }

college> db.students.updateMany({experience: {$elemMatch : {duration: {$lte:1}}}}, { $set : {"experience.$.neglect": true} })

{

name: 'Pradyumna'
hobbies: ['Singing', 'Cricket']
bio: 'I am a coder'
experience: [
    {company: "TCS", duration: 1, neglect: true },
    {company: "TCS", duration: 2 },
    {company: "TCS", duration: 1 }
],

age : 15 }

if we want to make all the experience to add neglect: true then

college> db.students.updateMany({experience: {$elemMatch : {duration: {$lte:1}}}}, { $set : {"experience.$[].neglect": 1} })

{

name: 'Pradyumna'
hobbies: ['Singing', 'Cricket']
bio: 'I am a coder'
experience: [
    {company: "TCS", duration: 1, neglect: true },
    {company: "TCS", duration: 2, neglect: true },
    {company: "TCS", duration: 1, neglect: true }
],

age : 15 }

// We only want to add negct: true in those who have experience le to 1

college> db.students.updateMany({experience: {$elemMatch : {duration: {$lte:1}}}}, { $set : {"experience.$[e].neglect": 1} }, {arrayFileters: [{"e.duration": {$lte:1}}]})

{

name: 'Pradyumna'
hobbies: ['Singing', 'Cricket']
bio: 'I am a coder'
experience: [
    {company: "TCS", duration: 1, neglect: true },
    {company: "TCS", duration: 2},
    {company: "TCS", duration: 1, neglect: true }
],

age : 15 }

$pop, $pull are used to remove an element drom an array $push is used to add an element n an array $addToSet is used to add an element without any repetition!