mysql的安装
教程：
https://blog.csdn.net/lsrzhangmin/article/details/132492978?spm=100
1.2014.3001.5501
步骤：
1.官网下载或者wget,然后解压 -xf, 卸载mariadb yum -y install *mariadb
2. 确定 mysql-community-server 正常安装之后就可以开始配置
依次安装所需要的依赖包
3. 初始化 mysqld 服务 mysqld --initialize
4. 启动服务 systemctl start mysqld
注意：如果在启动时，出现以下的错误：
root@mysql1 \~\]# systemctl start mysqld Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details. 这是因为/var/lib/mysql目录权限不够 修改权限并启动mysql: \[root@mysql1 \~\]#setenforce 0 \[root@mysql1 \~\]# chown -R mysql:mysql /var/lib/mysql \[root@mysql1 \~\]# chmod -R 777 /var/lib/mysql \[root@mysql1 \~\]# systemctl start mysqld.service \[root@mysql1 \~\]# ps -ef \|grep mysq mysql 2396 1 6 10:03 ? 00:00:00 /usr/sbin/mysqld root 2443 1355 0 10:03 pts/0 00:00:00 grep --color=auto mysq \[root@mysql1 \~\]# cd /var/lib/mysql \[root@mysql1 mysql\]# ll 5. 添加开机启动列表 systecmctrl enable mysqld 6. 在 /var/log/mysqld.log 中找到初始密码，前后复制空格 cat /var/log/mysqld.log \| grep password 7. 登录管理 mysql -uroot -p 将复制的密码粘贴到输入密码的区域，实现登录 8. 设置新的密码 在MySQL内将密码修改为root mysql\> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root'; ## 数据库的管理 #### 数据库的对象 1）数据库系统 DBMS 2）数据库 DB 3) 表 table 4) 记录 record 5) 字段 field #### 1.数据库的操作 ###### 创建库: mysql\> create database test charset utf8; Query OK, 1 row affected, 1 warning (0.00 sec) mysql\> show databases; +--------------------+ \| Database \| +--------------------+ \| information_schema \| \| mysql \| \| performance_schema \| \| sys \| \| test \| +--------------------+ 5 rows in set (0.00 sec) ###### 删除库: mysql\> drop database test; Query OK, 0 rows affected (0.00 sec) mysql\> show databases; +--------------------+ \| Database \| +--------------------+ \| information_schema \| \| mysql \| \| performance_schema \| \| sys \| +--------------------+ 4 rows in set (0.01 sec) ###### 查看库: mysql\> show databases; +--------------------+ \| Database \| +--------------------+ \| information_schema \| \| mysql \| \| performance_schema \| \| sys \| +--------------------+ 4 rows in set (0.01 sec) #### 2.表的操作 ###### 选择库： mysql\> use mysql; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed ###### 查看表： mysql\> show tables; mysql\> use test; Database changed mysql\> show tables; Empty set (0.00 sec) ###### 创建表： 语法： create table 表名();  ###### 删除表： drop table 表名； ###### 新增列：在password后加一列 mysql\> ALTER TABLE \`test\`.\`user\` -\> ADD COLUMN \`realname\` VARCHAR(45) NULL AFTER \`password\`; Query OK, 0 rows affected (0.04 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql\> describe user; //查看表结构 +----------+-------------+------+-----+---------+----------------+ \| Field \| Type \| Null \| Key \| Default \| Extra \| +----------+-------------+------+-----+---------+----------------+ \| id \| int \| NO \| PRI \| NULL \| auto_increment \| \| username \| varchar(45) \| NO \| UNI \| NULL \| \| \| password \| varchar(45) \| NO \| \| NULL \| \| \| realname \| varchar(45) \| YES \| \| NULL \| \| +----------+-------------+------+-----+---------+----------------+ 4 rows in set (0.01 sec) ###### 修改列名：修改realname列名为zsxm mysql\> ALTER TABLE \`test\`.\`user\` -\> CHANGE COLUMN \`realname\` \`zsxm\` VARCHAR(45) NULL DEFAULT NULL ; Query OK, 0 rows affected (0.01 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql\> desc user; +----------+-------------+------+-----+---------+----------------+ \| Field \| Type \| Null \| Key \| Default \| Extra \| +----------+-------------+------+-----+---------+----------------+ \| id \| int \| NO \| PRI \| NULL \| auto_increment \| \| username \| varchar(45) \| NO \| UNI \| NULL \| \| \| password \| varchar(45) \| NO \| \| NULL \| \| \| zsxm \| varchar(45) \| YES \| \| NULL \| \| +----------+-------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec) ###### 删除列：删除zsxm列 mysql\> ALTER TABLE \`test\`.\`user\` -\> DROP COLUMN \`zsxm\`; Query OK, 0 rows affected (0.02 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql\> desc user; +----------+-------------+------+-----+---------+----------------+ \| Field \| Type \| Null \| Key \| Default \| Extra \| +----------+-------------+------+-----+---------+----------------+ \| id \| int \| NO \| PRI \| NULL \| auto_increment \| \| username \| varchar(45) \| NO \| UNI \| NULL \| \| \| password \| varchar(45) \| NO \| \| NULL \| \| +----------+-------------+------+-----+---------+----------------+ 3 rows in set (0.01 sec) #### 3.记录的操作 主服务器：新增，删除，修改操作比较多， 从服务器：查询操作较多 ###### 新增： insret into 表名 （字段列表名）values (字段值列表） mysql\> select \* from user; Empty set (0.00 sec) mysql\> insert into user (id,username,password) values(3,'zhangsan','zhangsan'); Query OK, 1 row affected (0.01 sec) mysql\> select \* from user; +----+----------+----------+ \| id \| username \| password \| +----+----------+----------+ \| 3 \| zhangsan \| zhangsan \| +----+----------+----------+ 1 row in set (0.00 sec) 如果不写字段列表名，values必须写所有的字段值并且字段类型要正确 mysql\> insert into user values(3,'wangwu','wangwu'); Query OK, 1 row affected (0.00 sec) ###### 删除： delete from 表名 where 条件; 不加条件的时候，整个表里面的数据都会被删除 mysql\> delete from user where username='zhangsan'; Query OK, 1 row affected (0.00 sec) mysql\> select \* from user; +----+----------+----------+ \| id \| username \| password \| +----+----------+----------+ \| 4 \| lisi \| lisi \| +----+----------+----------+ 1 row in set (0.00 sec) ###### 修改: mysql\> select \* from user; +----+----------+----------+ \| id \| username \| password \| +----+----------+----------+ \| 1 \| zhangsan \| zhangsan \| \| 2 \| lisi \| lisi \| \| 3 \| wangwu \| wangwu \| +----+----------+----------+ 3 rows in set (0.00 sec) mysql\> update user set password=123 where username='zhangsan'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql\> select \* from user; +----+----------+----------+ \| id \| username \| password \| +----+----------+----------+ \| 1 \| zhangsan \| 123 \| \| 2 \| lisi \| lisi \| \| 3 \| wangwu \| wangwu \| +----+----------+----------+ 3 rows in set (0.00 sec)