Mysql database literacy, do you really know what a database is

One 、 What is a database

database ​​（DataBase,DB）​​ Is a long-term storage in the computer 、 organized 、 Shared 、 Data collection under unified management . It is a computer software system that stores and manages data according to data structure . Database has two meanings ： The one who keeps the data “ Warehouse ”, And the methods and techniques of data management .

Two 、 What stage has the database gone through in its development

The development of database can be roughly divided into the following stages ： Manual management stage 、 File system phase 、 Database system phase 、 Advanced database stage .

3、 ... and 、 What are the characteristics of the database

The database is characterized by ： Implement data sharing , Reduce data redundancy ; Use a specific data type ; High data independence ; With unified data control function .

Four 、 What are the tables in the database

In a relational database , A two-dimensional database is a set of tables , A logical structure used to store and manipulate data . It consists of vertical columns and horizontal rows .

Rows are called records , It's the unit that organizes the data ;

Columns are called fields , Each column represents an attribute of the record , There is corresponding description information , Such as data type 、 Data width, etc .

5、 ... and 、 What is the data type in the database

The data type determines the storage format of data in the computer , Represents different types of information . Commonly used data types are integer data types 、 Floating point data type 、 Exact decimal type 、 Binary data type 、 date / Time data type 、 String data type .

6、 ... and 、 What is a primary key

Primary key ​​（Primary Key）​​ Also known as the main code , Used to uniquely identify each record in the table . You can define one or more columns in a table as the primary key , On the primary key column There can be no two lines of the same value , Can't be null .

7、 ... and 、 What is the technical composition of the database

The database system consists of hardware part and software part . Hardware is mainly used to store data in the database , Including computers 、 Storage devices, etc .

The software part mainly includes DBMS、 Support DBMS The operating system running , And support the access technology of multi language application development .

8、 ... and 、sql What kinds of languages are there

（1） Data definition language ​​（DDL）​​​：​​DROP​​​、​​CREATE​​​、​​ALTER​​ Such statements .

（2） Data operation language ​​（DML）​​​：​​INSERT​​​（ Insert ）、​​UPDATE​​​（ modify ）、​​DELETE​​（ Delete ） sentence .

（3） Data query language ​​（DQL）​​​：​​SELECT​​ sentence .

（4） Data control language ​​（DCL）​​​：​​GRANT​​​、​​REVOKE​​​、​​COMMIT​​​、​​ROLLBACK​​ Such statements .

For example, we use ​​CREATE​​ To create a table ;

Log in and copy

      
      

       
       CREATE TABLE YUNWEIJIA ( ID INT UNSIGNED, NAME VARCHAR ( 30 ), PRIMARY KEY ( ID ) );
      
      
      
      

       
       
1.
      
      

The above command means , Create a name called ​​YUNWEIJIA​​​ Table of , There are two fields , Namely ​​ID ​​​ and ​​NAME​​​, among ​​ID​​​ It's the primary key ,​​NAME​​ The length of cannot exceed 30;

Let's insert a piece of data into the new table ;

Log in and copy

      
      

       
       INSERT INTO YUNWEIJIA ( ID, NAME )
       
       
VALUES
       
       
  ( '1', 'weixin' );
      
      
      
      

       
       
1.
       
       
2.
       
       
3.
      
      

Then we insert a piece of data into our database ;

Reuse ​​SELECT​​ To view the contents of this database ;

Log in and copy

      
      

       
       SELECT ID, NAME FROM YUNWEIJIA WHERE ID = '1';
      
      
      
      

       
       
1.
      
      

Running results ：

Nine 、 Database provider

Different programming languages have different database access interfaces , Programming languages execute through these interfaces ​​SQL​​​ sentence , Database management . The main database access interfaces are ​​ODBC​​​、​​JDBC​​​、​​ADO.NET​​​ and ​​PDO​​.

ODBC

​​ODBC（Open Database Connectivity, Open database connection ）​​​ Technology for accessing different ​​SQL​​​ Databases provide a common interface .​​ODBC​​​ Use ​​SQL​​​ As a standard for accessing data . This interface provides maximum interoperability ： An application can access different ​​SQL​​​ Database management system ​​（DBMS）​​.

One is based on ​​ODBC​​​ The application does not depend on any ​​DBMS​​​, Not directly with ​​DBMS​​​ Dealing with , All database operations are performed by the corresponding ​​DBMS​​​ Of ​​ODBC​​​ Driver complete . in other words , Whether it's ​​Access​​​、​​MySQL​​​ still ​​Oracle​​​ database , All available ​​ODBC API​​​ Visit . thus it can be seen ,​​ODBC​​ The biggest advantage of is that it can handle all databases in a unified way .

JDBC

​​JDBC（Java Data Base Connectivity,Java Database connection ）​​ be used for Java A standard way for applications to connect to a database , It's one for execution SQL Of the statement Java API, It can provide unified access for a variety of relational databases , By a group Java Language written classes and interfaces .

ADD.NET

​​ADO.NET​​​ It's Microsoft. ​​.NET​​​ A set of object-oriented class libraries developed and designed under the framework for interacting with data sources .​​ADO.NET​​​ Provides a pair of relational data 、​​XML​​ And access to application data , Allow interaction with different types of data sources and databases .

PDO

​​PDO（PHP Data Object）​​​ by ​​PHP​​ Accessing the database defines a lightweight 、 A consistent interface , Provides a data access abstraction layer . such , Whatever database you use , You can query and get data through consistent functions .

Ten 、 What are the components of a database system

• database ： A place for storing data .
• Database management system ： Software for managing databases .
• Database management system ： Software for managing databases .

database

A database may contain many files , A database system usually contains many databases .

Database management system （DBMS）

It's user creation 、 The software used to manage and maintain a database , Between the user and the operating system , Unified management of the database .​​DBMS​​ Can define data storage structure , The operation mechanism of providing data , Maintain database security 、 Integrity and reliability .

Database applications

The use of database application can meet the higher requirements of data management , It can also make the data management process more intuitive and friendly . The database application is responsible for working with ​​DBMS​​​ communicate , Access and management ​​DBMS​​ Data stored in , Allow users to insert 、 modify 、 Delete DB Data in .

11、 ... and 、mysql How to understand

​​MySQL​​​ Is a small relational database management system . With other large database management systems （ for example ​​Oracle​​​、​​DB2​​​、​​SQL Server​​​ etc. ） comparison ,​​MySQL​​​ Small scale 、 Limited function , But it's small 、 Fast 、 The cost is low , And the functions provided are enough for slightly complex applications , These characteristics make ​​MySQL​​ Become the world's most popular open source database .

Twelve 、mysql The version is mainly divided into why

• ​​MySQL Community Server（ Community server ）​​： This version is completely free , But the government doesn't provide technical support .
• ​​MySQL Enterprise Server（ Enterprise server ）​​​： It can provide data warehouse applications for enterprises with high cost performance , Support ​​ACID Business ​​ Handle , Provide complete submission 、 Roll back 、 Crash recovery and row level locking . But this version needs to be used for a fee , Official telephone technical support .

1. MySQL 8.0 Is the latest development of stable （GA） Release series , Is a series that will perform new functions ;
2. MySQL 8.0 It's more stable （GA） Release series . Re release only for vulnerability repair , There are no new features that will affect stability .
3. MySQL 5.7 It's the previous stable （ product quality ） Release series . Only for serious vulnerability fixes and security fixes , No addition will affect the important functions of the series .

13、 ... and 、mysql What are the advantages

1. Speed ： Fast running speed .
2. Price ：​​MySQL​​ It's free for most individuals .
3. Easy to use ： Compared with the setting and management of other large databases , It's less complicated , Easy to learn .
4. Portability ： Able to work on many different system platforms , for example ​​Windows​​​、​​Linux​​​、​​UNIX​​​、​​Mac OS​​ etc. .
5. Rich interfaces ： Provided for ​​C、C++、Eiffel、Java、Perl、PHP、Python、Ruby​​​ and ​​Tcl​​​ Languages like ​​API​​.
6. Support query language ：​​MySQL​​​ Standards can be used ​​SQL​​​ Grammar and support ​​ODBC​​ Applications for .
7. Security and connectivity ： Very flexible and secure access and password system , Allow host based authentication . When connecting to the server , All password transmissions are encrypted , This ensures password security . because MySQL It's Networked , So it can be accessed anywhere on the Internet , Improve the efficiency of data sharing .

fourteen 、mysql What are the command line tools

1. ​​mysqld​​​：​​SQL​​​ daemon （​​MySQL​​ Server process ）. It must be after the program is run , The client can access the database by connecting to the server .
2. ​​mysqld_safe​​​： Server startup script . stay ​​UNIX​​​ and ​​NetWare​​​ Recommended in ​​mysqld_safe​​​ To start up ​​mysqld​​​ The server .​​mysqld_safe​​ Added some security features , For example, when an error occurs, restart the server and write the runtime information to the error log file .
3. ​​mysql.server​​： Server startup script . This script is used to use the 、 Run the script that starts the service 、 The system running the directory . It calls ​​mysqld_safe​​ To start up ​​MySQL​​ The server .
4. ​​mysql_multi​​： Server startup script , You can start or stop multiple servers installed on the system .
5. ​​myisamchk​​​： Used to describe the 、 Check 、 Optimization and maintenance ​​MyISAM​​ Table utility .
6. ​​mysqlbug​​​：​​MySQL​​​ Defect report scripts . It can be used to ​​MySQL​​ The email system sends defect reports .
7. ​​mysql_install_db​​​： This script is created with default permissions ​​MySQL​​ Authorization Form . Usually just on the system First installation ​​MySQL​​ When the once .

15、 ... and 、mysql What are the utility programs on the client side

1. ​​myisampack​​​： Compress ​​MyISAM​​ surface , A tool to generate smaller read-only tables .
2. ​​mysql​​​： Interactive input ​​SQL​​ Statements or command line tools that execute them in batch mode from files , It is also our most commonly used tool .
3. ​​mysqlaccess​​： Check access hostname 、 User name and database combination permission script .
4. ​​mysqladmin​​： A client program that performs administrative operations , for example Create or delete a database 、 Overload authorization table 、 Refresh the table to the hard disk and reopen the log file .​​mysqladmin​​ It can also be used to retrieve versions 、 process , And the status of the server .
5. ​​mysqlbinlog​​： A tool for reading statements from binary logs . Include executed statements in the binary log file , Can be used to help the system Recover from a crash .
6. ​​mysqlcheck​​： Check 、 Repair 、 Analyze and optimize table maintenance clients for tables .
7. ​​mysqldump​​​： take ​​MySQL​​​ Dump the database to a file （ for example ​​SQL​​​ Sentence or ​​tab​​ Separator text file ） The client program for .
8. ​​mysqlhotcopy​​​： When the server is running , Fast backup ​​MyISAM​​​ or ​​ISAM​​ Table tools .
9. ​​mysqlimport​​​： Use ​​LOAD DATA INFILE​​ Client programs that import text files into related tables .
10. ​​mysqlshow​​： Display database 、 surface 、 Column and the client program that indexes the relevant information .
11. ​​perror​​​： Display system or ​​MySQL​​ Tools for error code meaning .

sixteen 、mysql8.0 and 5.7 comparison , What features have been added

1. The data dictionary （ Used to store information about database objects ）
2. Atomic data definition statement （ Even if the server pauses during operation , Transactions will also be committed , And keep the applicable changes to the data dictionary 、 Storage engine and binary log , Or roll back the transaction ）
3. Security and account management （8.0 Can support roles , Administrators uniformly add and delete , There is no need to specify permissions for each user ）
4. Resource management （ Support the creation and management of resource groups , It also allows the threads running in the server to be assigned to specific resource groups ）
5. ​​InnoDB​​ Add on function
6. Character set support （ The default character set has been changed ​​latin1​​​ by ​​utf8mb4​​​. The ​​utf8mb4​​​ There are several new collations for the character set , These include ​​utf8mb4_ja_0900_as_cs​​）
7. enhance ​​JSON​​ function
8. Data type support
9. Query optimization
10. Common table expression
11. Window function
12. Statistical histogram （ Using histogram , Users can make statistics of data distribution for one column of a table , Especially for fields without indexes . This can help the query optimizer find a better execution plan ）
13. Backup the lock （ The new type of backup lock is allowed during online backup ​​DML​​​, At the same time, prevent operations that may cause inconsistent snapshots . The new backup lock is set by ​​LOCK INSTANCE FOR BACKUP and UNLOCK INSTANCE​​​ Grammar support . The administrator has ​​BACKUP_ADMIN​​ Permission to use these statements .）

thus , In this paper, the end . 

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