MongoDB Database introduction 、 Installation and basic use

One 、 Preface

1.1 Introduction to basic concepts

We are in the process of learning , Access to a large number of databases , for example Sql Server、Mysql、Mybatis etc. , They all belong to traditional relational databases , That is, data based on two-dimensional table .

What we learn today is MongoDB Database is not a traditional relational database , It is between relational database and non relational database , Yes no relational database has the most functions , Most like a relational database NoSQL（Not Only Sql） database , With key-value stored , Do not follow the basic requirements of traditional relational databases 、 Table structure and other features .

NoSQL It is mainly used to help solve big data query problems , It is of great significance in the era of big data .

1.2 Nosql Compared with relational databases

Unstructured database has no rows 、 The concept of column , Use JSON Store the data , aggregate Equivalent to... In a relational database surface , The document is equivalent to That's ok .

Two 、 install

2.1 download

visit MongoDB Official website ：www.mongodb.com Download it , Here is the download link of community version https://www.mongodb.com/try/download/community.

Pay attention to choosing the correct version 、 Platforms and packages , Here is the download 5.0.9 edition 、Windows platform 、MSI Installation package .

Foreign websites are not necessarily easy to download , The following is what I uploaded CSDN resources （ free ）:

1. mongodb-windows-x86_64-5.0.9-signed.msi
2. mongodb-macos-x86_64-5.0.9.tgz

2.2 install

1. Double click Install Package

2. All the way to the next step

3. Custom installation

4. Select installation location

5. Select the data storage location （ It is recommended to choose a disk with large space ）

6. Don't choose to install MongoDB Compass（ If the network is bad, the download will fail , You can install it later ）

7. Click on the install

2.4 environment variable

1. Copy MongoDB Of bin Path to directory , I am here ：D:MongoDb\bin

2. Right click on the left side of the folder “ This computer ”, choice “ attribute ”： This computer -> attribute

3. Create a new environment variable

4. Open terminal input ：mongo, The output is as follows （ It could be different , I am here 5.0.8 edition ）

PS E:\Code> mongo
MongoDB shell version v5.0.8
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session {
     "id" : UUID("bdfd1afc-e66b-4211-bf91-16e80d6845d5") }
MongoDB server version: 5.0.8
================
Warning: the "mongo" shell has been superseded by "mongosh",
which delivers improved usability and compatibility.The "mongo" shell has been deprecated and will be removed in
an upcoming release.
For installation instructions, see
https://docs.mongodb.com/mongodb-shell/install/
================
---
The server generated these startup warnings when booting:
        2022-07-16T07:08:30.841+08:00: Access control is not enabled for the database. Read and write access to data and configuration is unrestricted
---
---
        Enable MongoDB's free cloud-based monitoring service, which will then receive and display
        metrics about your deployment (disk utilization, CPU, operation statistics, etc).

        The monitoring data will be available on a MongoDB website with a unique URL accessible to you
        and anyone you share the URL with. MongoDB may use this information to make product
        improvements and to suggest MongoDB products and deployment options to you.

        To enable free monitoring, run the following command: db.enableFreeMonitoring()
        To permanently disable this reminder, run the following command: db.disableFreeMonitoring()
---
>

3、 ... and 、 Easy to use

First, enter... At the terminal mongo Establish a database connection , The command can be executed later ！ Be careful , The following commands are continuous , Suggest sequential learning .

3.1 show dbs

view the database , Just installed MongoDB There will be three basic databases , Don't delete them , as follows ：

> show dbs
admin   0.000GB
config  0.000GB
local   0.000GB

3.2 use db_name

Selecting a database you want to operate requires use db_name Instructions

> use db_posts
switched to db db_posts

Be careful ：

Here you can choose a nonexistent database , If so, it can be used to create a new database .

But at this time, the database has not been created , You need to insert data before creating a database .

3.3 insert()

insert() Method is used to insert data into the specified set , for example ：

> db.user.insert({
    username:' Xiao Ming ',age:12})
WriteResult({
     "nInserted" : 1 })

Be careful ：

The database cannot insert data directly , You need to aggregate Insert data （ file ）, there user It's just a set .

If user If it doesn't exist, a new one will be created user surface , The format of data insertion is standard JSON Format .

At this time, a new database is created db_posts And a new user table user, And insert a data into the table . If we use show dbs You can see the database db_posts 了 .

> show dbs
admin     0.000GB
config    0.000GB
db_posts  0.000GB 
local     0.000GB

3.4 show collections

Check how many tables are in the current database （ aggregate ） Need to use show collections command ：

> show collections
user

3.5 find()

Use db. Table name .find() You can query all the data in the table ：

> db.user.find()
{
     "_id" : ObjectId("62d285cbb9789c8ce412e785"), "username" : " Xiao Ming ", "age" : 12 }

We can insert a few more pieces of data ：

> db.user.insert({
    username:' Xiaohong ',age:99})
WriteResult({
     "nInserted" : 1 })
> db.user.insert({
    username:' cockroach ',age:999})
WriteResult({
     "nInserted" : 1 })
> db.user.find()
{
     "_id" : ObjectId("62d285cbb9789c8ce412e785"), "username" : " Xiao Ming ", "age" : 12 }
{
     "_id" : ObjectId("62d28835b9789c8ce412e786"), "username" : " Xiaohong ", "age" : 99 }
{
     "_id" : ObjectId("62d2884cb9789c8ce412e787"), "username" : " cockroach ", "age" : 999 }

3.6 drop()

Deleting a collection requires db. Table name .drop()：

> db.user.drop()
true
> show collections
>

3.7 dropDatabase()

Delete database , There is an embarrassing place here , Databases without collections are not displayed , That is to say, in the implementation of dropDatabase The database was no longer visible . Anyway, this syntax is to delete the database , Don't care about these details .

> db.dropDatabase()
{
     "ok" : 1 }
> show dbs
admin   0.000GB
config  0.000GB
local   0.000GB