mysql的安装+数据库的管理

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)

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