db -> collection -> document

db.users.insetOne({name: "Bipul"})

db.users.find().sort({name: -1}).limit(2)

db.users.find().sort({age: -1, name: -1}).limit(3) //sort by age in rev order(99->0) if same age then sort by name in rev order

like where in sql db.users.find({age: 21}) //unlike js find it returns all users whose age is 26

like select in sql db.users.find({name: "Bipul"}, {name: 1, age: 1, _id: 0})

db.users.find({name: "Bipul"}, {age: 0})

mongoose -> Schema, query, model we can add methods, validations, queries , virtuals and middlewares to the schema

userSchema.methods.sayHi = function(){ clg (HI ${this.name}) } //used on instances

userSchema.methods.findByName = function(){ return this.find({name: new RegExp(name, 'i')}) } //used on models

userSchema.methods.byName = function(){ return this.where({name: new RegExp(name, 'i')}) } // chained on methods in models

userSchema.virtual("namedEmail").get(function(){ return ${this.name} } )// only in code not saved in db

middleware

userschema.pre('save', function(next){ this.updatedAt = Date.now() next() })

//cant use this, as it passes the doc that is saved userSchema.post('save', function(doc, next){ doc.sayHi() next() })

https://github.com/akashshyamdev/mongoose-query-methods-cheatsheet

https://drive.google.com/file/d/1ZEcnJi6oglVQ5qkVnumYdPXvyVHBk7Ck/view?usp=sharing

https://mongoosejs.com/docs/queries.html