About MySQL Database

I. Knowledge of the database

1. The origin of the database

Previously known data is stored in a file, but a file can only exist on one machine, but in reality, all the data is not stored on a machine.

(1) In reality it is impossible to put all the applications on one machine

Assuming that all applications are installed on only one machine, if it collapses, it means that the data disappears permanently, so no one will do so unless idiot. And the performance of a machine is limited, some people think of the device to add hardware, the key is how you add hardware to improve performance, to the end certainly will reach a limit, so, it is not advisable to install all the applications on a machine.

(2) Security of data is not guaranteed

If the data is stored on a single machine, the sharing of data is bound to be inconsistent. Therefore, try not to store all the data on one machine.

(3) Concurrency effect

You must write a socket server to manage the files on this machine (database servers) and then write a socket client to complete the following functions:

#1. Remote connection (concurrent support) #2. Open File # #. Read and write (locking) #4. close File

Summarize these points:

　　　　Before writing any program, you need to write a program based on the network operation of a file on a host (socket server and client program), so some people will write such a program as a special
Processing software, this is the origin of MySQL and other database management software, but MySQL solves not only the problem of data sharing, as well as query efficiency, security and a series of problems, in short, the programmer from the number
According to the management of the release, focus on their own program logic to write.
II. Overview of the database
1. The concept of data
The record symbol used to describe the state of everything in the world is called data, it can be pictures, videos, files and so on.
2. The concept of a database
A database is a warehouse that holds all the data, except that it is located on a computer and is stored in a certain format.
3. Database management System (DB Management System-dbms)

In order to organize and store data scientifically and efficiently, it uses a system software---database management system , such as MySQL, Oracle, SQLite, Access, MS SQL Server.

The relationship between database server, data management system, database, table and record--focus on understanding

Entries: 1 Big Fat 324245234 22 (information from multiple fields makes up a record, that is, a row in the file)

Table: student,scholl,class_list (i.e. file)

Database: Oldboy_stu (that is, folder)

Database management system: such as MySQL (is a software)

Database server: One computer (high memory requirements)

Summarize:

Database server-: Running database management software

Database management software: Management-Database

Database: A folder for organizing files/tables

Table: A file that is used to hold multiple lines of content/Multiple records

Third, MySQL introduction

What is 1.mysql?

MySQL is a relational database management system, is a socket-based C/s architecture software.

Client software: MySQL comes with >> such as MySQL command, mysqldump command, etc.

Python modules >> such as Pymysql

2. Classification of database management software

It is divided into two main categories:

　　　　Relationship type: As Sqllite,db2,oracle,access,sql server,mysql, NOTE: SQL statements are common

Non-relational : Mongodb,redis,memcache

Can be understood as:

　　　　relational databases require a table structure

    The non-relational database is key-value stored, without a table structure
Four, installation
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V. Software Management
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Vi. Initial knowledge of SQL statements
MySQL Server software is mysqld to help us manage folders and files, provided that we as users, we need to download the MySQL client, or other modules to connect to the MYSQLD,
Then use the syntax format specified by the MySQL software to submit your own commands, to achieve the management of folders or files. The syntax is SQL (structured query Language, which is the structured Queries language)

the SQL language is primarily used to access data, query data, update data, and manage relational database systems, which are developed by IBM. There are 3 types of SQL language:#1, DDL Statement    database Definition language: Database, table, view, index, stored procedure, such as Create DROP ALTER#2, DML Statement    database manipulation language: Inserting data insert, deleting data Delete, updating data update, querying data Select#3, DCL Statement    database Control Language: For example, to control access rights for a user grant, REVOKE

Statement Type

About MySQL Database