1. NoSQL数据库与SQL数据库的对应关系
2. 在Node中使用MongoDB
3. 新建记录
4. ObjectID
5. 查找记录
6. Update
7. Delete

NoSQL数据库与SQL数据库的对应关系

1. Table - Collection
2. Row/Record - Document
3. Column - Field

1. 在/etc/yum.repos.d/下创建mongodb-org-4.4.repo,内容如下:

       [mongodb-org-4.4]
       name=MongoDB Repository
       baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.4/x86_64/
       gpgcheck=1
       enabled=1
       gpgkey=https://www.mongodb.org/static/pgp/server-4.4.asc
   

2. 然后使用yum直接安装 sudo yum install -y mongodb-org

1. systemctl start mongod
2. systemctl stop mongod
3. systemctl status mongod

在Node中使用MongoDB

const mongodb = require("mongodb");
//客户端
const mongoClient = mongodb.MongoClient;

//数据库的URL
const url = 'mongodb://106.54.215.164:27017';

//使用的数据库, 可以自定义
const databaseName = 'weathers';

//三个参数, 第一个是URL, 第二个是配置, 第三个是成功回调函数
mongoClient.connect(url, {useNewUrlParser: true}, function (error, client) {
    if (error) {
        console.log("AN error");
    }
    console.log(url, "Connected.");
});

(node:14928) 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.

新建记录

mongoClient.connect(url, {useNewUrlParser: true}, function (error, client) {
    if (error) {
        console.log("AN error");
    }
    console.log(url, "Connected.");

    //指定某个数据库, 如果没有就会创建
    const db = client.db(databaseName);

});

const db = client.db(databaseName);

//然后需要找一个表(collection), 向其中插入一条记录(Document)
db.collection('users').insertOne({
    name: "Cony",
    age: 6
});

db.collection('users').insertOne({
    name: "Jenny",
    age: 36
}, (error, result) =>{
    if (error) {
        return console.log("Unable to insert");
    }
    console.log(result.ops);
});

db.collection("clusters").insertMany(
    [{good:'working',bepatient:'tocony'},{good:'working2',bepatient:'tocony2'},{good:'working22',bepatient:'tocony22'}],
    {},
    (error, result) =>{
        if(error)
            return console.log("Unable to insert");
        console.log(result.ops);
    }
)

ObjectID

{
    "_id" : ObjectId("5f35554763e5c44d507585dc"),
    "name" : "Cony",
    "age" : 6
}

1. 4字节的时间戳, 有了这个, 无需特意保存每条记录的生成时间
2. 5字节的随机值
3. 3字节的计数器, 初始化为一个随机的值

const mongodb = require("mongodb");
const mongoClient = mongodb.MongoClient;
const ObjectID = mongodb.ObjectID;

const {MongoClient, ObjectID} = require("mongodb");

const id = ObjectID();

console.log(id);

const id = ObjectID("aabbccaabbccaabbccaabbcc");
MongoClient.connect(url, {useNewUrlParser: true}, function (error, client) {
    if (error) {
        console.log("AN error");
    }
    console.log(url, "Connected.");

    const db = client.db(databaseName);

    db.collection("customId").insertOne(
        {
            _id: id,
            game: "Baldur's Gate 3",
            release: 'unknown'
        }, {}, (error, result) => {
            if (error) {
                return console.log("Unable to insert");
            }
            console.log(result.ops);
        }
    );
 });

const id = ObjectID();
console.log(id.id);
console.log(id.toHexString());
console.log(id.getTimestamp());

<Buffer 5f 36 08 db 28 6f 69 3b 08 cc e0 d4>
5f3608db286f693b08cce0d4
2020-08-14T03:45:31.000Z

查找记录

db.collection("users").findOne({
        name: 'Cony',
        age:6
    }, (e,user)=>{
        if (e) {
            return console.log(e);
        }
        console.log(user);
    })

db.collection("users").find({
        age: 36
    }).toArray((error, users) => {
        console.log(users);
});

db.collection("users").find({
        age: 36
    }).count((error, count) => {
        console.log(count);
});

Update

1. filter, 用于选择要更新哪些document
2. update, 如何更新
3. options, 设置选项
4. callback, 永远的回调函数

const updatePromise = db.collection("users").updateOne(
    {
        age: 36
    }, {
        $set: {
            age: 37
        },

    }
);

updatePromise.then((result) => {
    console.log(result)
}).catch(()=>{console.log("Error")});

Delete

const deletePromise = db.collection("users").deleteOne(
    {
        age: 36
    }, {
    }
);

deletePromise.then((result) => {
    console.log(result)
}).catch(()=>{console.log("Error")});