Summary of basic knowledge of MySQL database

xxxxxx 2020-11-07 16:43:51
summary basic knowledge mysql database

This paper deals with MySQL The basic knowledge of database is summarized and combed , The main contents are knowledge database 、 Common database rankings 、SQL And DDL Operating the database . I hope that after you read it , Be able to understand the concept of database , And be able to use SQL Statement operation database .

1、 Know the database

(1) How data is stored

a. Memory : Fast , But it can't be preserved forever , Data is temporary state .

b. file : Data can be stored permanently , But it's not convenient to manipulate the data , You need to query some data .

c. database : Data can be stored permanently , Fast query speed , The management of data is convenient , But it takes up resources , Need to buy .

(2) The concept of databases

A database is a warehouse for storing data , It's essentially a file system , Or in the form of files on the server computer . And all relational databases can use common SQL Statement Management .

2、 Common database rankings

a.MySQL: Open source free database , Small database , Has been Oracle Acquired .MySQL6.x The version also began to charge . later Sun The company acquired MySQL, and Sun The company was again Oracle Acquisition .

b.Oracle: A large database of charges ,Oracle Products of the company .

c.DB2:IBM The company's database products , Rechargeable . Often used in banking systems .

d.SQL Server:MicroSoft A database of medium-sized companies that charge .C#、.net Such language is often used .

e.SQLite: Embedded small database , It's used on the mobile phone , Such as :Android.

3、SQL The concept of

SQL(Structured Query Language) Chinese is also called structured query language . It is a query specification for all relational databases , Different databases support . As a general database operating language , It can be used in different databases . Different databases SQL There are some differences in sentences .

4、DDL Operating the database

(1) Create database

a. Create database directly db1

create database db1;

b. Judge whether it exists , If it doesn't exist, create the database db2

create database if not exists db2;

c. Create a database and specify the character set as gbk

create database db3 default character set gbk;

(2) view the database

Press tab Key can automatically complete the keyword

—— View all databases

show databases;

—— View the definition information of a database

show create database db3;

show create database db1;

(3) modify the database

Modify the default character set of the database


Specific operation :

take db3 The character set of the database is changed to utf8

alter database db3 character set utf8;

(4) Delete database

Delete database Syntax

DROP DATABASE Database name ;

Specific operation :

Each row SQL Statement needs to be selected for execution , Can press F9

Delete db2 database

drop database db2;

(5) Using a database

View the database in use

SELECT DATABASE(); One used mysql Global functions in

Use / Switch database

USE Database name ;

Specific operation :

—— View the database in use

select database();

—— Change the database to be used

use db4;

That's all MySQL Summarize and sort out the basic knowledge of database , Does everybody understand ? Zhengzhou men's gynecology hospital ranking list : Zhengzhou infertility hospital :


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