Mongodb command summary

The basic chapter （ Can solve the problem of 80% The problem of ）:

1. MongoDB Overview 、 Application scenarios 、 Download mode 、 Connection mode and development history, etc

2. MongoDB data type 、 Key concepts and shell Commonly used instructions

3. MongoDB Various additions to documents 、 to update 、 Delete operation summary

4. MongoDB Summary of various query operations

5. MongoDB Summarize the various operations of the column

6. MongoDB Summary of index operations in

Advanced :

7. MongoDB Summary of aggregation operations

8. MongoDB Import and export of 、 Backup recovery summary

9. MongoDB Summary of user management

10. MongoDB Copy （ Replica set ） summary

11. MongoDB Slice summary

12. MongoDB meet spark（ Integration ）

13. MongoDB Internal storage principle

Other :

14. python3 operation MongoDB Various cases of

15. MongoDB Command summary

One . MongoDB Command help system

See the detailed usage of each command , have access to ：db.listCommands()

More detailed help commands for database operation ：db.help()

Operate on the collection of the specified database 、 Management and monitoring ：db.mycoll.help()

Two . Basic commands and examples

（ One ） Basic commands

Displays the databases on the current database server ：show dbs

Switch to the specified database pagedb Of ：use pagedb

Show all collections in the database ：show collections or show tables

View the status of the database server ：db.serverStatus()

Query the specified database statistics ：db.stats()

（ Two ） Commonly used DDL and DML

understand DML、DDL、DCL、DQL Major name

SQL Language can be divided into four categories ： Data manipulation language DML, Data definition language DDL, Data control language DCL, Data query language DQL.

DML（data manipulation language  Data manipulation language ）:  They are UPDATE、INSERT、DELETE, Just like its name , this 4 Command is the language used to operate the data in the database 

DDL（data definition language  data ( library ) Define language ）:  The main orders are CREATE、ALTER、DROP etc. ,DDL Mainly used to define or change tables （TABLE） Structure , data type , The initialization of links and constraints between tables , Most of them use it when creating tables 

DCL（Data Control Language  Data control language ）:  It's the database control function . Is used to set or change the database user or role permissions statement , Include （grant,deny,revoke etc. ） sentence . By default , Only sysadmin,dbcreator,db_owner or db_securityadmin Wait for the people to have the power to carry out DCL

DQL（Data Query Language  Data query language ）： It's the database control function , Include  select  sentence 

Create database mydatabase: use mydatabase; ( Just switch , Not to create )

Create set student
db.createCollection("student",{capped:true,size:1000,max:100})

Have a try ,max be equal to 3 perhaps size be equal to 1, What will happen? ？

Insert update record

surface (student)

 {
    _id:1,classid:1,age:18,name:"little1",love:["football","swing","cmpgame"]}
 {
    _id:2,classid:2,age:19,name:"little2",love:["play"]}
 {
    _id:3,classid:2,age:20,name:"little3"}
 {
    _id:4,classid:1,age:21,name:"little4"}
 {
    _id:5,classid:1,age:22,name:"little5",opt:"woshisheia"}
 {
    _id:6,classid:2,age:23,name:"23little4"}

Insert

 db.student.save({
    _id:1,classid:1,age:18,name:"little1",love:["football","swing","cmpgame"]})
 db.student.save({
    _id:2,classid:2,age:19,name:"little2",love:["play"]})
 db.student.save({
    _id:3,classid:2,age:20,name:"little3"})
 db.student.save({
    _id:4,classid:1,age:21,name:"little4"})
 db.student.save({
    _id:5,classid:1,age:22,name:"little5",opt:"woshisheia"})
 db.student.save({
    _id:6,classid:2,age:23,name:"23little4"})

perhaps

db.student.insert([
 {
    _id:1,classid:1,age:18,name:"little1",love:["football","swing","cmpgame"]},
 {
    _id:2,classid:2,age:19,name:"little2",love:["play"]},
 {
    _id:3,classid:2,age:20,name:"little3"},
 {
    _id:4,classid:1,age:21,name:"little4"},
 {
    _id:5,classid:1,age:22,name:"little5",opt:"woshisheia"},
 {
    _id:6,classid:2,age:23,name:"23little4"},
 ])

summary ： Once the set starts capping mode , When max Or is it size beyond , New data over old data

Look up a record / Multiple records

Query out name by little1 The data of : db.student.find({name:"little1"})

From the second search , Find three : db.student.find().skip(1).limit(3)

The query is greater than 19 Less than or equal to 21：db.student.find({age:{$gt:19,$lte:21}})

Query out age Odd data ( Yes 2 The rest is 1 Is an odd number )：db.student.find({age:{$mod:[2,1]}})

Query the existence of opt Field data ：db.student.find({opt:{$exists:true}})

The query does not exist opt Field data ：db.student.find({opt:{$exists:false}})

Query out name Not for little2 The data of ：db.student.find({name:{$ne:"little2"}})

Query out age by 16,18,19 The data of ：db.student.find({age:{$in:[16,18,19]}})

Query out age Not for 16,18,19 The data of ：db.student.find({age:{$nin:[16,18,19]}})

Query out love There are three data ：db.student.find({love:{$size:3}})

Query out name Not in litt Initial data ：db.student.find({name:{$not:/^litt.*/}})

Inquire about age=“”>20 The data of ：db.student.find({age:{$gt:20}})

Press age Ascending ：db.student.find().sort({age:1})

Press age Descending ：db.student.find().sort({age:-1})

Number of query data ：db.student.find().count()

Delete record

Delete age by 20 The data of ：db.student.remove({age:20});

Create index

Create index age：db.student.ensureIndex({"age":1})

Query index ：db.student.getIndexes()

Delete index ：db.student.dropIndex({"age" : 1})

Count the number of set records ：db.student.count()

Delete the collection student：db.student.drop()

Delete database mydatabase：db.dropDatabase()

（ 3、 ... and ） security management

Start in secure authentication mode

Add users

Safety certification

（ Four ） The data backup 、 Recovery and migration management

Back up all databases

Back up the specified database

Back up a collection in a database

Restore all databases

Recover data from a database

Recover data from a collection of a database

towards MongoDB Import data

from MongoDB Derived data

（ 5、 ... and ） Remote connection management

be based on mongo Realize remote connection
mongo —host 192.168.17.129 —port 27017

（ 6、 ... and ） polymerization
Calculate the average age of each class

db.student.aggregate([
 {
    
    $group: {
    
      _id: "$classid",
      avg_age: {
    
        $avg: "$age"
      }
    }
  }
])

Calculate the average age of the whole class

db.student.aggregate([
 {
    
    $group: {
    
      _id: null,
      avg_age: {
    
        $sum: "$age"
      }
    }
  }
])

( 7、 ... and ) MapReduce

Calculate the average age of each class

Grouping statistics (MapReduce):

var mapfun = function(){
    emit(this.classid,this.age);}
var reducefun = function(key, values){
    
    var total=0; 
    for(var i=0;i<values.length;i++){
    
        total += values[i];
    }
    return {
     classid: key, age_avg: total/values.length };
}
db.student.mapReduce(
      mapfun,
      reducefun,
      {
     out: "student_res" }
)

Query statistical results ( Count the number of people by class )：db.student_res.find()

Count the number of students in each class
Grouping statistics (MapReduce):

var mapfun = function(){
    emit(this.classid,1);}
var reducefun = function(key, values){
    
     return Array.sum(values);
}
db.student.mapReduce(
      mapfun,
      reducefun,
      {
     out: "student_sta" }
)

Query statistical results ( Count the number of people by class )：db.student_sta.find();