What is CRUD?

Create, Read, Update, and Delete (CRUD) are the four basic functions that models should be able to do, at most.

Error message: Process finished with exit code -1073741819 (0xC0000005)

问题描述：
idea中启动项目报 Process finished with exit code -1073741819 (0xC0000005) ，如图所示：

问题解决：
原因：经过多方查证，问题最终定位在金山词霸2016上，如果开启了金山词霸的划译功能，就会出现此错误，具体原理有待研究。在关闭金山词霸时，有时idea也会自动关闭。

​ 解决：关掉金山词霸，或者把金山词霸的划译功能关掉，然后重启idea，再运行项目就没问题了。经过尝试，发现只要在IDEA第一次打开并运行的时候，没有开启金山词霸的划译功能，那么之后就算开启也不会有问题。所以如果一定需要用金山，就先打开idea运行项目，在打开金山，或者直接把金山的划译功能关掉就可以了。

！！！注意：金山词霸划译与idea2018.3+版本不兼容

MONGODB

structure

Data in MongoDB is made up of three types of components: databases, collections, and documents. The database sits at the top of the hierarchy, collections at the next level, and documents at the bottom.

img

operation:

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const mongoose = require("mongoose");
const { stringify } = require("querystring");

//open the connection
mongoose.connect("mongodb+srv://dxexperiments-user:DrEuMg7KfFImh774@dxvignettes.vtnenqy.mongodb.net/");

// this lays out the foundation for every new fruit document that will be added to the database
const fruitSchema = new mongoose.Schema({
    name: String,
    rating:{
        type:Number,
        min: 1,
        max: 10
    },
    review: String
});

// first parameter, name of the collection(mongodb will convert this string into a pluralize form to create your collection); so we created a new collection called Fruits
// second parameter: It is the schema of the collection.
const Fruit = mongoose.model("Fruit", fruitSchema);


// creating fruit document from Fruit model, means the document need to stick to this schema
const fruit = new Fruit({
    name:"apple",
    rating: 6,
    review:"well, average."
});

//save fruit document into the Fruist collection inside of the DATABASE
// fruit.save();

const personSchema = new mongoose.Schema({
    name: String,
    age:Number
});


const grape = new Fruit({
    name: "grape",
    rating: 7,
    review: " I really like it"
});

const kiwi = new Fruit({
    name: "kiwi",
    rating: 6,
    review: " I really like it"
});

const pineapple = new Fruit({
    name: "pineapple",
    rating: 9,
    review: " I really like it"
});
// Fruit.insertMany([kiwi,grape,pineapple]);

Fruit.find().exec()
  .then((fruits) => {
      //close the connection
    mongoose.connection.close();
    fruits.forEach((fruit) => {
      console.log(fruit.name);
    });
  })
  .catch((error) => {
    console.error('Error retrieving fruits:', error);
  });

data validation with mongoose:

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const fruitSchema = new mongoose.Schema({
    name: 
    {
        type: String,
        required: [true, 'Why no name?']
    },
    rating:
    {
        type:Number,
        min: 1,
        max: 10
    },
    review: String
});

delete and update

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Fruit.updateOne({_id:"648dc4fdd4b6dda3193f73b3"}, {name: "change"});
Fruit.deleteOne({name: "kiwi"})
  .then(() => {
    console.log("Kiwi deleted successfully");
  })
  .catch((error) => {
    console.error("Error deleting kiwi:", error);
  });
  
  
  Person.deleteMany({name: "Dan"})  .then(() => {
    console.log("Dan deleted successfully");
  })
  .catch((error) => {
    console.error("Error deleting kiwi:", error);
  });