Mongodb installation and basic operation

MongoDB Installation

Use docker install

Download mirroring ：

• docker pull mongo:4.4.8（ recommend , Download the specified version ）

• docker pull mongo:latest ( Download the latest version by default )

Look at the mirror image ：

docker images

• You can see mongo It has been downloaded

Start the mirror ：

docker run -d --restart=always -p 27017:27017 --name mymongo -v /data/db:/data/db mongo:4.4.8

• -d Background operation
• –restart=always docker Container start up mongo And start The same is true of shutdown
• -name Specify the name of the container
• -v Bound with a file on the disk

Into the container :

docker exec -it mymongo /bin/bash

Enter into mongo The client of

mongo

MongoDB Concept of analytical

No matter what database we learn we should learn the basic concepts, right , stay mongodb The basic concept is documentation 、 aggregate 、 database , Let's introduce in detail , The following table will help you understand more easily Mongo Some of the concepts in ：

SQL The term / Concept	MongoDB The term / Concept	explain / explain
database	database	database
table	collection	Database table / aggregate
row	document	Data record row / file
column	field	Data field / Domain
index	index	Indexes
table joins		Table joins ,MongoDB I won't support it
primary key	primary key	Primary key ,MongoDB Automatically put _id Field sets the primary key

MongoDB Common operations

（1）Help Check the command prompt

db.help();

（2） Switch / Create database

use test

If the database doesn't exist , Then create the database , Otherwise switch to the specified database

（3） Query all databases

show dbs;

（4） Delete the currently used database

db.dropDatabase();

（5） View currently used databases

db.getName();

（6） Show the current db state

db.stats();

（7） At present db edition

db.version();

（8） View the current db Link machine address

db.getMongo();

Commonly used instructions ：

Let's create a database first

use test

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1 INSERT（ newly added ）

Insert into User Collection

db.User.save({name:‘zhangsan’,age:21,sex:true})

Inquire about User All documents in the collection

db.User.find()

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2 Remove（ Delete ）

remove() Used to delete single or all documents , The deleted document cannot be recovered

• Delete all ：db.User.remove({})
• Appoint id Delete ：db.User.remove(id)
• Specify conditions to delete ：db.User.remove({‘name’:‘zhangsan’})

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3 UPDATE ( modify )

• first { } Is the condition
• The second brace Is the content that needs to be modified

** Example ：**db.User.update({name:“lucy”}, {$set:{age:100, sex:0}})

Update() There are a few parameters to note .

db.collection.update(criteria, objNew, upsert, mult)

• criteria: Conditional expressions that need to be updated

• objNew: Update expression

• upsert: Such as FI The label record does not exist , Whether to insert a new document .

• multi: Whether to update multiple documents .

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4 QUERY（ Inquire about ）

4.1 WHERE

stay mongo in How do we use conditional queries ？

** grammar ：**db.User.find ({“filed”, value })
Example ： db.User.find({name:“ Zhang San ”})

convert to sql ： select * form User where name = ‘ Zhang San ’

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4.2 FIELDS

In normal development , You only need to query some fields in a set ？ So how can we achieve such a business ？

• first {} Express What conditions to query It's up there where
• the second {} Express To be found field The value is 1

** grammar ：**db.User.find ( { } , { “filed” , value })

** Example ：**db.User.find( { name : “ Zhang San ” } , { ‘name’ : 1 } )

convert to sql： select name from User where name = ‘ Zhang San ’

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5 SORT

stay MongoDB Use in sort() Method to sort the data ,sort() Method can be used to specify the sorting field by parameter , And use 1 and -1 To specify how to sort , among 1 Arrange... In ascending order , and -1 It's for descending order .

** Example ：**db.User.find().sort({‘age’:1})

The conversion SQL ：select * from User order by age desc

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6 Intercept

stay MongoDB Use in limit() Method to read a specified amount of data ,skip() Method indicates the line from which to read

Example ： db.User.find().skip(1).limit(2)

Corresponding SQL： select * from User skip 1 limit 2

All the data in the set ： There are two of them

The first line starts reading Read to the end of the second line

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7 in（ contain ）

Example ： db.User.find({age:{$in:[21,26,32]}})

** The conversion SQL：**select * from User where age in (21, 26, 32)

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8 COUNT（ The statistical number of rows ）

Example ： select count(*) from User where age >20

The conversion SQL： db.User.find({age:{$gt:20}}).count()

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9 OR ( perhaps )

age yes 20 perhaps 30 All meet the conditions Be similar to |

Example ： select * from User where age = 21 or age = 30

The conversion SQL： db.User.find({$or:[{age:21}, {age:30}]})

10 aggregate（ polymerization ）

MongoDB Middle polymerization (aggregate) It's mainly used to process data ( Such as the statistical average , Make a peace, etc ), And return the calculated data result . It's kind of similar sql Statement count(*)

Insert test data

db.article.insert({title: ‘MongoDB Overview’,description: ‘MongoDB is no sql database’,by_user: ‘runoob.com’,url: ‘http://www.runoob.com’,tags: [‘mongodb’, ‘database’, ‘NoSQL’],likes: 100})

db.article.insert({title: ‘NoSQL Overview’,description: ‘No sql database is very fast’,by_user: ‘runoob.com’,url: ‘http://www.runoob.com’,tags: [‘mongodb’, ‘database’, ‘NoSQL’],likes: 10})

db.article.insert({title: ‘Neo4j Overview’,description: ‘Neo4j is no sql database’,by_user: ‘Neo4j’,url: ‘http://www.neo4j.com’,tags: [‘neo4j’, ‘database’, ‘NoSQL’],likes: 750})

Common aggregate expressions

expression	describe	Example
$sum	Calculate the sum	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", num_tutorial : { $sum:"$likes"}}}])
$avg	Average	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", num_tutorial : { $avg:"$likes"}}}])
$min	Get the minimum value of all documents in the collection .	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", num_tutorial : { $min:"$likes"}}}])
$max	Get the maximum value of all documents in the collection .	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", num_tutorial : { $max:"$likes"}}}])
$push	Insert values into an array in the result document .	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", url : { $push:"$url"}}}])
$addToSet	Insert values into an array in the result document , But don't create copies .	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", url : { $addToSet:"$url"}}}])
$first	Get the first document data according to the sorting of resource documents	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", first_url : { $first:"$url"}}}])
$last	Get the last document data according to the sorting of resource documents	db.mycol.aggregate([{ KaTeX parse error: Expected '}', got 'EOF' at end of input: …roup : {_id : "by_user", last_url : { $last:"$url"}}}])

11 Indexes

Indexing can usually be greatly improved Query efficiency , If there is no index ,MongoDB When reading data, you must scan Collection Of Every File and select those records that meet the query conditions . This scan Full set The query efficiency is Very low Of , Especially when dealing with large amounts of data , Queries can take tens of seconds or even minutes , The performance of this website is Very deadly Of . Indexes Is a special data structure , The index is stored in a collection of data that is easy to read through , An index is an index of a database table One or more columns A structure that sorts the values of .

db.User.createIndex({“name”:1})

In the syntax **name**** The value is the index field that you want to create ,

1** Creates an index in ascending order for the specified , If you want to create the index in descending order specify as -1 that will do