MongoDB ＜＜ connection to database and creation of data

Keywords: Javascript Database ECMAScript MongoDB

1.mongodb official website

MongoDB: the application data platform | MongoDB

2. Go to the official website of MongoDB and download MongoDB, MongoDB compass and Mongodb--database--tools

3. The operation of the MongoDB database by nodejs needs to rely on the third-party package mongoose of nodejs

Terminal instruction: npm install mongoose

Run PowerShell cd as an administrator to the directory where the file is located. If MongoDB is not enabled

Start using the net start mongodb command

//Introduce mongoose module
const mongoose = require('mongoose');
// console.log(mongoose);

//todo connection database
mongoose.connect('mongodb://localhost/test001')
    .then(() => console.log('Database link succeeded'))
    .catch(erro => console.log('connection failed'))

7. In the vscode integration terminal, cd to the directory where the file is located, and use the nodemon 'node 02.js' command to open the file

8. Set set set rules, create sets and apply rules

//todo set collection rules
const courseSchema = new mongoose.Schema({
    name: String,
    author: String,
    isPublished: Boolean
});
// todo creates collections and applies rules
// todo 1. Collection name '' 2. Collection rule
const Course = mongoose.model('Course', courseSchema);

9. Two ways to create a collection instance document

// todo is the first way to create a collection instance document
const course = new Course({
    name:'xiaoguo',
    author:'aaa',
    tags:['node','backend'],
    isPublished:false
})
// Save data in database
course.save();



//The second method of todo creates a document without using course.save(), which will be automatically saved into the database
Course.create({
    name:'xiaowei',
    author:'sh',
    isPublished:true
},(erro,data)=>{
    console.log(erro);
    console.log(data)
});
//promise objects are also supported
Course.create({
    name:'xiaoli',
    author:'zz',
    isPublished:true
}).then(data=> console.log(data))
.catch(erro=>console.log(erro))

10. Query all documents in the user collection and return an array

// todo queries all documents in the user collection and returns an array
Course.find()
.then(result =>{console.log(result)})

11. Query a document in the user collection through the ID field and return an array

// todo returns an array by querying a document in the user collection through the ID field
Course.find({
_id:"619b0f75dc5e07d1b9924ee9"
})
.then(result =>{console.log(result)})

12. Find the document according to the condition. If the condition is not written, return the first document in the database and return an object

// todo finds documents according to conditions. If no conditions are written, the first document in the database returns an object
Course.findOne({
    name:'xiaowei'
})
.then(result=>console.log(result))

13. Find document based on range criteria $gt min $lt Max

// todo finds documents based on range criteria
Course.find({
    age: { $gt: 20, $lt: 50 }
})
.then(result => console.log(result))

14. Query contains

// todo finds documents based on range criteria
Course.find({
    name: { $in: ['xiao'] }
})
.then(result => console.log(result))

15. Select the fields to query and sort them. The default ascending and descending order is plus one-

// todo select the fields to query (in ascending order)
Course.find().select('name age')
//The reverse order is. sort('-age') (descending)
.then(result => console.log(result))

sixteen Skip skip the first two data limits limit the number of queries

// todo skip skip the first two data limits limit the number of queries
Course.find().skip(2).limit(2)
.then(result => console.log(result))

seventeen Find a document and delete it. The return value is the deleted document. If multiple documents are matched, only the first one will be deleted

// todo finds a document and deletes it. The return value is the deleted document. If multiple documents are matched, only the first one will be deleted
Course.findOneAndDelete({
   _id:"619b0f75dc5e07d1b9924ee9"
})
.then(result=>console.log(result))

eighteen Delete multiple documents Return an object {n: number of deleted documents ok: 1 (deleted successfully)}

// todo deletes multiple documents and returns an object {n: number of deleted documents ok: 1 (deletion succeeded)}
Course.deleteMany({
   _id:"619b0f75dc5e07d1b9924ee9"
})
.then(result=>console.log(result))

nineteen When updating a single document, two objects are passed. The first object is the second value of the query condition

// todo updates two objects in a single document. The first object is the second value to be changed in the query condition
Course.updateOne(
{name:'xiaoguo'},
{name:'xiaoguoguo'}
)
.then(result=>console.log(result))

twenty Update multiple documents and transfer two objects. The first object is the second value of the query condition to be changed

// todo updates multiple documents and passes two objects. The first object is the second value to be changed in the query condition
Course.updateMany(
{},
{age:18}
)
.then(result=>console.log(result))

twenty-one Set mongoose authentication

For String type fields required: [true, 'error description'] Required fields