db.order.insertOne({item:12,qty:2,size:"m",details:{title:"Banana"}})
db.order.updateOne(
  { item: 12 }, // filter condition
  { $set: { qty: 13 } } // update operation using $set
)

db.order.updateOne(
  {item:12},
  {$set: {discount:2}}
  )

db.employees.insertMany([
  {empId: 1, name: 'Clark', dept: 'Sales' },
  {empId: 2, name: 'Dave', dept: 'Accounting' },
  {empId: 3, name: 'Ava', dept: 'Sales' },
  {empId: 4, name:"anusuiya", dept:'Deginer'},
]);

db.salary.insertMany([
  {eid:1,salary:15000},
  {eid:2,salary:25000},
  {eid:3,salary:35000},
  {eid:4,salary:45000},
  ])
  
  db.salary.updateMany(
    {eid:{$gte:3}},
    {$set:{tdss:30}}
  )
 

db.employees.deleteOne(
  {empId:1}
  )

db.order.insertOne({
  item_id:2,qty:3,size:"s",price:78
})

 db.order.insertOne({
   item_id:3,qty:12,size:"s",price:99
 })

// db.order.find()

//db.employees.find({dept: 'Sales'});


//db.order.find({item:12})

db.order.updateMany(
  {size:"s"},
  { $set: { tchild:"Avaliable"} }
  )

db.salary.aggregate([{
  $match:{salary:{$gt:36000}}
}])

db.salary.aggregate([{
  $group:{
    _id:0,
    totAddSalry:{$sum:"$salary"}
  }
}])

// db.employees.aggregate([{  $match:{   empId: { $gt: 2 }  } } ])
//db.employees.find({dept: 'Sales'});
// db.employees.aggregate([{  $match:{    empId:1  } } ])
// db.order.find()
// db.employees.find()


db.employees.aggregate([
  {
    $lookup:{ from:"salary",localField:"empId",foreignField:"eid",as:"salaryInfo"}
  },
  {
    $addFields: {
      salaryInfo: { $ifNull: ["$salaryInfo", [{ eid: null, salary: null }]] }
    }
  }
]) 


db.employees.aggregate([
  {
    $lookup:{ from:"salary",localField:"empId",foreignField:"eid",as:"Mysal"}
  }
]) 

db.salary.aggregate([
  {
    $lookup:{from:"employees",localField:"eid",foreignField:"empId",as:"empInfo"}
  },
   {
    $addFields:{ empInfo: { $ifNull: ["$empInfo", [{ msg:"deleted by deletedOne" }]] } }
  }
  ])
  
   db.salary.updateMany([
    {eid:{$gte:3}},
    {$set:{tds:20}}
  ])

  db.salary.find()
  
  db.salary.aggregate([
    {$group:{_id:null, count:{ $sum:1 }}}
    ])
    
    db.salary.aggregate([
      {$group:{_id:null,Salsum:{$sum:"$salary"}}}
      ])
    
    db.employees.aggregate([
      {$group:{_id:null, sum:{$sum:1}}},
      
      
      ])
  
  db.salary.aggregate([
    {$match:{salary:{$gte:35000}}},
    {
     $lookup:{from:"employees",localField:"eid",foreignField:"empId",as:"SalEmp"}
    },
    {
     $project:{ _id:0,eid:1,salary:1,SalEmp:{empId:1,name:1}}
    }
    
    
    ])
    
    db.salary.countDocuments({})
    db.employees.count()
    
    //db.colectionName.update({matchQuery},{updateDocument},{optional})
    
    db.employees.update(
      {empId:10},{$set:{empId:7,name:"vijay",dept:"Agreculture"}},{upsert:true}
      )
      
      db.employees.find();
      
      
      
      db.mycomment.insert([
        
        {"status": "Approved", "comment": "Great work!", "username": "user1"},
    {"status": "Pending", "comment": "Needs review", "username": "user2"},
    {"status": "Rejected", "comment": "Incomplete", "username": "user3"},
    {"status": "Approved", "comment": "Well done!", "username": "user4"},
    {"status": "Pending", "comment": "Almost there", "username": "user5"},
    {"status": "Rejected", "comment": "Not satisfactory", "username": "user6"},
 
        
        ])
        
       
        
        db.mycomment.find({status:{$in:["Rejected","Approved"]}})
        db.mycomment.aggregate([
          {$match:{status:{$in:["Pending","Approved"]}}}
          
          ])
        
         db.mycomment.aggregate([
          {$match:{status:"Pending"}}
          ])