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Mongodb database

2020-11-08 17:47:00 【Qing comes from orchid】

1. Database overview and environment building

1.1 Why use a database

The data in the dynamic website is stored in the database
The database can be used to persist the user information collected by the client through forms
Database software itself can manage data efficiently

1.2 What is a database

A database is a warehouse for storing data , Data can be stored in an orderly and classified manner . It's language independent software , Can pass API To operate it . Common database software is : mysql. mongoDB. oracle.

1.3 MongoDB Download and install the database

Download address : https://www.mongodb.com/download-center/community

1.4 MongoDB Visualization software

MongoDB Visual operation software , It's a way to operate a database using a graphical interface .

1.5 Database related concepts

Multiple data warehouses can be included in a database software , Each data warehouse can contain multiple data sets , Every Data sets can contain multiple documents ( Specific data ).

The term	interpretative statement
database	database ,mongoDB Multiple databases can be created in database software
collection	aggregate , A collection of data , It can be understood as JavaScript In the array
document	file , A specific piece of data , It can be understood as JavaScript Objects in the
field	Field , Attribute names in the document , It can be understood as JavaScript Object properties in

1.6 Mongoose The first 3 Tripartite package

Use Nodejs operation MongoDB The database needs to depend on Node.js The first Tripartite package mongoose
Use npm install mongoose Command download

1.7 start-up MongoDB

Run in the command line tool net start mongoDB You can start MongoDB, otherwise MongoDB Will not be able to connect .

1.8 Database connection

Use mongoose Provided connect Method to connect to the database .

MongoDB The return is promise object

mongoose.connect('mongodb://localhost/playground')
     .then(() => console.log(' Database connection successful '))
     .catch(err => console.log(' Database connection failed ', err));

When connecting to the database, if you are prompted with the following information , stay content Method to add a second parameter , { useNewUrlParser: true }

(node:15596) DeprecationWarning: current URL string parser is deprecated, and will be removed in a future version. To use the new parser, pass option { useNewUrlParser: true } to MongoClient.connect.

If you are prompted (node:14524) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.

Continue to add { useUnifiedTopology: true }, Separated by commas

//  Introduce third-party modules mongoose
const mongoose = require('mongoose');
// 1、 Connect to database playground, If there is no such database , Automatically created 
mongoose.connect('mongodb://localhost/playground', {
        useUnifiedTopology: true,
        useNewUrlParser: true
   })
    //  Successful connection 
   .then(() => console.log(' Database connection successful '))
    //  The connection fails 
   .catch(err => console.log(err, ' Database connection failed '));