Installation and use of NoSQL database

（ One ） complete Redis Installation and use . Complete database insertion , Delete , And inquiry .

  Redis It's a key value （key-value） The storage system , That is, key value pair non relational database , and Memcached similar , At present, it is being adopted by more and more Internet companies .Redis As a high-performance key value database , It not only makes up for memcached This kind of key value storage is insufficient , And in some cases, it can play a good complementary role to the relational database .Redis Provides Python、Ruby、Erlang、PHP client , Easy to use .

① Use hadoop The user login ubuntu kylin, stay windows System use FileZilla Files in compressed format redis-5.0.5.tar.gz Transfer saved in “/home/hadoop/ download ” Under the table of contents , Now unzip the package to the path /usr/local Next .

② take redis-5.0.5.tar.gz Unzip the file and save it to “/usr/local/” Under the table of contents .
③ take redis-5.0.5 Rename it to redis, And put redis The permission of the directory is given to hadoop user .

④ Get into “/usr/local/redis” Catalog , Input compilation and installation Redis.


⑤ Already completed Redis Installation , Now on Redis The server .

⑥ New terminal , start-up Redis client . After the client connects to the server , Will be displayed “127.0.0.1:6379>” Command prompt information for , Represents the... Of the server IP The address is 127.0.0.1, Port is 6379. Now you can perform simple operations , such as , Set the key to ”hello”, The value is ”world”, And take out the key as ”hello” The corresponding value of . thus Redis Installation and operation succeeded , Then you can operate Redis database .

Redis The database is based on <key,value> In the form of data storage , Save the data of the table Redis Database time ,key and value The determination method of is as follows ：

* key= Table name : Primary key value : Name 
* value= The column value  

⑦ insert data ： towards Redis Insert a piece of data , Just design it first key and value, And then use set Command to insert data . for example , stay Course Insert a new course into the table “ big data ”,4 credits , The operation commands and results are shown in the following figure .

⑧ Delete data : Redis There are special commands to delete data ——del command , The command format is “del key ”. therefore , If you want to delete a previously added course “ big data ”, Just enter the command “del Course:8:Cname”, As shown in the figure below , When the input “del Course:8:Cname” when , return “1”, Description: a piece of data has been successfully deleted .

⑨ Query data ：Redis The simplest way to query is to use get command . Input get Command query , Output is empty , This indicates that the data was deleted successfully .

（ Two ）MongoDB Installation and use .

    complete MongoDB The basic shell command . MongoDB Is a database based on distributed file storage , Between relational and non relational databases , Non-relational databases are the most versatile , Most like a relational database . The data structure it supports is very loose , Is similar to json Of bson Format , Therefore, more complex data types can be stored .Mongo The biggest feature is that the query language he supports is very powerful , Its syntax is somewhat similar to that of an object-oriented query language , You can almost implement most of the functionality of a relational database single table query , It also supports indexing data .
① Use apt-get Command to install online MongoDB, It can avoid many inexplicable problems .
Command line sudo apt-get install mongodb Downloadable installation MongoDB, The default installed version is MongoDB 2.6.10, But at the moment, MongoDB Has been upgraded to 3.2.8, You can install by adding software sources 3.2.8 edition .

a. First open the terminal , Import public key To package manager

b. establish MongoDB List of files .

c. Update package manager , install MongoDB.


d. installation is complete MongoDB in the future , Enter the following command at the terminal to view MongoDB edition .

②MongoDB Start up and shut down .

③ Get into MongoDB Of shell Command mode . The default database to connect to is test database , Before that, be sure to start MongoDB, Otherwise, an error will occur , The successful operation after startup is as follows .

④ Common operation command
Database correlation
show dbs: Show database list
show collections： Displays the collection in the current database （ Similar to tables in relational databases table）
show users： Show all users
use yourDB： Switch the current database to yourDB
db.help() ： Display the database operation command
db.yourCollection.help() ： Show set operation commands ,yourCollection Is the collection name

MongoDB There is no command to create a database , If you want to create a “School” The database of , First run use School command , Then do some operations （ Such as ： Create aggregation sets db.createCollection('teacher')）, So you can create one called “School” The database of .

⑤ With a School Database, for example , stay School Create two sets in the database teacher and student, Also on student The basic operations of adding, deleting, modifying and querying the data in the collection （ aggregate Collection Equivalent to tables in a relational database table）.
a. Switch to School database ( Switch to School database .MongoDB No pre creation required School database , It will be automatically created when used )

b. establish Collection( Create an aggregate set .MongoDB In fact, when inserting data , The corresponding set will also be automatically created , There is no need to predefine the set )

c. Similar to database creation ,MongoDB The collection will also be automatically created when inserting data . There are two ways to insert data ：insert and save.

Insert data succeeded

_id identical , Update data

_id identical , Insert the failure , No operation .

d. The structure of the added data is loose , As long as it is json The format can be , Column properties are not fixed , According to the added data . Define the data before inserting , You can insert multiple pieces of data at once .

e. Run the above example ,student Automatically created , explain MongoDB There's no need to predefine collection , After first inserting data ,collection Will automatically create .

⑥ Find data
a. db.student.find() Check all records . amount to ：select * from student

b. db.student.find({sname: 'zhangsan'}) Inquire about sname='zhangsan' The record of . amount to ： select * from student where sname='zhangsan'

c. db.student.find({},{sname:1, sage:1}) Query specified column sname、sage data . amount to ：select sname,sage from student.

sname:1 Said to return to sname Column , Default _id Fields are also returned , You can add _id:0（ Do not return _id） It's written in {sname: 1, sage: 1,_id:0}, Will not return to the default _id Field

d. db.student.find({sname: 'zhangsan', sage: 22})
and And conditional query . amount to ：select * from student where sname = 'zhangsan' and sage = 22

e. db.student.find({$or: [{sage: 22}, {sage: 25}]})
or Conditions of the query . amount to ：select * from student where sage = 22 or sage = 25

f. db.youCollection.find(criteria, filterDisplay) criteria：
Query criteria , Optional filterDisplay： Filter and display some data , If the specified column data is displayed , Optional （ When choosing , The first parameter cannot be omitted , If the query condition is empty , You can use {} Do a placeholder ）

⑦ Modifying data db.youCollection.update(criteria, objNew, upsert, multi )

criteria: update Query criteria for , similar sql update In the query where hinder objNew : update Object and some updated operators （ Such as $set） etc. , It can also be understood as sql update In the query set hinder .

upsert : If it doesn't exist update The record of , Whether insert objNew,true Insert for , The default is false, Do not insert .
multi: mongodb The default is false, Update only the first record found , If this parameter is zero true, According to the conditions to find out all the records updated . Default false, Only the first matched data is modified .

among criteria and objNew Is a required parameter ,upsert and multi Optional parameters . db.student.update({sname: 'lisi'}, {$set: {sage: 30}}, false, true)
amount to ：update student set sage =30 where sname = 'lisi';

⑧ Delete data db.student.remove({sname: 'chenliu'}) amount to ：delete from student where sname='chenliu'

⑨ Delete the collection

⑩ sign out shell Command mode
Input exit perhaps Ctrl+C sign out shell Command mode

（ 3、 ... and ） Use Java API Yes MongoDB Visit .

①Java MongoDB Driver drive jar The package has been saved to ’/home/hadoop/ download /’ Under the table of contents .

② open Eclipse, newly build Java Project.

Introduce driver package mongodb-driver-3.8.0.jar.

newly build Class Average_grade


Empty Average_grade.java Code inside , Then enter the complete execution set in this file student Code for adding, deleting, modifying, and querying .

After the program is run, it will be in the bottom “Console” The operation result information is displayed in the panel .

Each time the program is executed , You can go back to shell Mode view results . Such as ： stay eclipse After performing the update operation , stay shell Mode input db.student.find(), You can see student All the data of the collection .

（ Four ）Redis And traditional Mysql What is the difference between databases ？

①mysql Is a relational database , It is mainly used to store persistent data , Store data on a hard disk , Slow read speed .redis yes NOSQL, This is a non relational database , It is also a cache database , Store data in cache , Cache read speed is fast , Can greatly improve the operation efficiency , But the storage time is limited .
②mysql Relational databases as persistent storage , The relative weakness is that every time you request access to the database , They all exist I/O operation , If the database is accessed repeatedly and frequently .
First of all ： You spend a lot of time chaining databases , As a result, the operating efficiency is too slow ;
second ： Repeated database access can also lead to overloading of the database , Then the concept of caching is derived .
③ A cache is a buffer for data exchange （cache）, When the browser executes the request , First of all, search in the cache , If there is , Just get ; Otherwise, access the database . The advantage of caching is fast reading speed .
④redis Database is a cache database , Used to store frequently used data , This reduces the number of times you access the database , Improve operational efficiency .

（ 5、 ... and ）MongoDB What are the characteristics of , and Mysql What is the difference between databases ？

characteristic ：
Mongodb It's a non relational database (nosql), It's a document database . The document is mongoDB The basic unit of data in , Like rows in a relational database , Multiple key value pairs placed together in an orderly manner is the document , The grammar is a little bit similar javascript Object oriented query language , It's a set oriented , Schema free document database .
storage ： Virtual memory + Persistence . Query statement ： It's unique Mongodb Query mode of . Suitable for the scene ： A record of the incident , Content management or blog platform, etc .
Architectural features ： Through the replica set , And sharding to achieve high availability .
Data processing ： The data is stored on the hard disk , Just the data that needs to be read frequently will be loaded into memory , Store data in physical memory , So as to achieve high-speed reading and writing .
Maturity and breadth ： Emerging databases , Less mature ,Nosql Database is closest to relational database , More perfect DB One of , The applicable population is growing .

difference ：
MongoDB There's also one big drawback , It takes up a lot of space , stay MongoDB When data is added, deleted, or modified frequently , If the record changes , For example, the data size has changed , At this time, it is easy to generate some data fragments , The result of fragmentation , One is that indexes have performance problems .
MySQL And MongoDB They are all open source common databases , however MySQL It's a traditional relational database ,MongoDB It's a non relational database , It's also called document database , It's a kind of NoSQL The database of . They have their own advantages , The key is to see where it's used . So those we know well SQL（ Full name Structured Query Language） The statement does not apply to MongoDB 了 , because SQL Statement is the standard language for relational databases .