mysql database
1. Overview of mysql
1. MySQL is an open source relational database server software. MySQL is a relational database management system developed by the Swedish MySQL AB company and is a product of Oracle. MySQL is one of the most popular relational database management systems. In terms of WEB applications, MySQL is one of the best RDBMS (Relational Database Management System) application software.
MySQL is a relational database management system. A relational database stores data in different tables instead of putting all data in one large warehouse, which increases speed and flexibility.
The SQL language used by MySQL is the most commonly used standardized language for accessing databases. MySQL software adopts a dual licensing policy and is divided into community version and commercial version. Due to its small size, fast speed, low total cost of ownership, especially open source, MySQL is generally chosen as the website for the development of small, medium and large websites. database.
*Currently developed and maintained by Oracle Corporation
*Official site: http://ww.mysql.com
2. Features of mysql
* Multi-threading, multi-user
* Based on C/S (client/server) architecture
* Simple and easy to use, fast query speed
* Safe and reliable
Compile and install mysql on centos
(1), Mysql download link: https://downloads.mysql.com/archives/community/
(2) Add the mysql user and user group
groupadd mysql && useradd -r -g mysql mysql to mysql
(3) Create the data directory of the database and grant permissions to mysql
mkdir /data/mysql -p
chown -R mysql:mysql /data/mysql
（4）、修改mysql的配置文件
vim /etc/my.cnf
[mysqld]
bind-address=0.0.0.0
port=3306
user=mysql
basedir=/usr/local/mysql
datadir=/data/mysql
socket=/tmp/mysql.sock
log-error=/data/mysql/mysql.err
pid-file=/data/mysql/mysql.pid
#character config
character_set_server=utf8mb4
symbolic-links=0
explicit_defaults_for_timestamp=true
(4) Unzip the tar package of mysql, move the package to /usr/local/mysql, and initialize
tar xf mysql-8.0.32-linux-glibc2.12-x86_64.tar.xz #Unzip
mv mysql-8.0.32-linux-glibc2.12-x86_64 /usr/local/mysql
cd /usr/local/mysql/bin/
./mysqld --defaults-file=/etc/my.cnf --basedir=/usr/local/mysql/ --datadir=/data/mysql/ --user=mysql --initialize
(5) Create database shortcut command and start
cp /usr/local/mysql/support-files/mysql.server /etc/init.d/mysql #Add mysql system service
chkconfig -add mysql #Add system service
systemctl start mysql #Start mysql
ln -s /usr/local/mysql/bin/mysql /usr/bin/ #Create a soft connection for the mysql command
cat /data/mysql/mysql.err #View the root password of mysql
Check the running status of mysql
Ps -ef |grep mysql
Netstat -natp |grep 3306
(6) Log in to mysql
Mysql -uroot -p Log in to mysql
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3. Basic commands of mysql
1. Connect and log in to the MySQL operating environment
mysql -u username [-p password]
Mysql command parameters:
-V #View database version
-h #Specify login database ip address
-P #Specify database port (default is 3306)
-u #Specify login user
2. Mysql backup command mysqldump
ln -s /usr/local/mysql/bin/mysqldump /usr/bin/ #Create mysqldump command soft connection
mysqldump -u [user] -p [password] [library to be backed up] > /Backup to what #mysqldump command format
mysqldump -uroot -p mysql > /home/mysql_bak_2023_0502.sql #Library name
Mysqldump command parameters:
-u #Specify user
-p #Enter password
Example:
To back up the database, you can create a separate user.
For example, I need to back up the test database.
The steps are as follows:
(1) Create a back user
create user back@'%' identified by '123456';
(2) Grant the permission to backup the test library
grant process on . to back@'%';
grant process on test.* to back@'%';
show grants for back@‘%’;
(3) Back up the test library
mysqldump -uback -p test > /home/666.sql.
Enter the password: 123456
3. Modify the user password command mysqladmin
mysqladmin -u username -p password “newpwd” #Command format
mysqladmin -u root -p password “123456”
Mysqladmin command parameters:
-u #Specify user
Password #Specify new password
4. Basic management commands of database
(1) View the database structure
(1) View the database
SHOW DATABASES
(2) View the data table information in the database
USE database name #switch to the database
SHOW TABLES #view the tables of the database
(3) Display the structure (fields) of the data table
DESCRIBE [database name.] table name
(2) Creation and deletion of database
(1) Create a new database
create database database name
(2) Create a table in the test library.
Use test
CREATE TABLE table name (field definition...)
create table users (user_name CHAR(16) NOT NULL, user_passwd CHAR(48) DEFAULT '', PRIMARY KEY (user_name)) ;
(3) Delete the table
DROP TABLE database name. table name
drop tables test.users;
(4) Delete the database
DROP DATABASE auth;
drop database test;
(3) Inserting and querying data records
(1) Insert new data records into the data table.
First create the database and table
create database test; #Create the test library
use test; #Switch to the test library
create table users(user_name CHAR(16)NOT NULL, user_passwd CHAR(48) )DEFAULT '', PRIMARY KEY (user_name)); # Create users table
INSERT INTO table name (field 1, field 2, ...) VALUES (field 1 value, field 2 value, ...)
insert into users(user_name,user_passwd) values('zhangsan','123456');
insert into users(user_name,user_passwd) values('yzq','123456');
insert into users(user_name,user_passwd) values('wangwu','123456')
(2) Find data records that meet the conditions from the data table
SELECT field name 1, field name 2... FROM table name WHERE conditional expression
select * from users; #Query all information in the users table
Select user_name,user_passwd from users where user_name=”lisi”\G; #where condition query, query user_name = lisi
Select user_name,user_passwd from users where user_passwd = '123456' and user_name = 'yzq'; #Multi-condition query, query user_name =yzq and user_passwd= 123456
(4) Modify data records
(1) Modify and update data records in the data table
UPDATE table name SET field name 1 = value 1 [, field name 2 = value 2] WHERE conditional expression
UPDATE auth.users SET user_passwd=PASSWORD('666666') WHERE user_name='lisi'; #Modify users' lisi's user_passwd=666666
(2) Delete wangwu’s information in the users table
DELETE FROM table name WHERE conditional expression
delete from test.users where user_name = 'wangwu';
5. Optimization of mysql database
(1) Modify the root password
Method 1: Modify the root user's password in the database
alter user 'root'@'localhost' identified by '666666'
flush privileges; #Refresh the permission table
Method 2:
Enter outside the database:
mysqladmin -u root -p password "123456"
and enter the old password
(2) For security reasons, delete empty users whose user names and passwords are empty
select user,host,password from mysql.user where user=''; #Query users whose passwords are empty
delete from mysql.user where user= ''; #Delete users with empty passwords
6. Mysql database maintenance database and user permission commands
grant --authorize
revoke --revoke
identified by Set password
(1), set user permissions (when the user does not exist, create a new user) The data usage of version 8.0 is different format
: GRANT permission list ON database name. table name TO user Name@source address [ IDENTIFIED BY 'password' ]
| Format description name | Parameters and description |
|---|---|
| Permission list | Select (check), insert (insert), update (change), all (all permissions) comma separated all – all permissions |
| Source address | % (match all) can be domain name, IP address, etc. |
| Password options | If omitted, the user password is empty |
Taking the MySQL version after 8.0 as an example,
you need to create a user first:
create user test@'%' identified by '123456';
grant all privileges on test.* to test@'%';
(2) View user permissions
SHOW GRANTS FOR username@source address;
show grants for test@'%';
(3) Revoke user permissions
revoke permission list ON database name.table name from username@source address
revoke all on test.* from test@'%';
