mysql的设置更改root密码、连接、常用命令

13.1 设置更改root密码

更改环境变量PATH ，增加mysql绝对路径
首次直接使用mysql会提示‘该命令不存在’，原因是还没有将该命令加入环境变量，如果要使用该命令，需要使用其绝对路径：/usr/local/mysql/bin/mysql，为了方便，先将其加入系统环境变量：

[root@taoyuan ~]# export PATH=$PATH:/usr/local/mysql/bin/

mysql命令路径暂时加入环境变量，系统重启后该变量会失效，若要永久生效，需要将其加入环境变量配置文件：

vi /etc/profile

#在配置文件最后 把上面的命令加

#执行source命令生效
[root@taoyuan ~]# source /etc/profile

首次登陆

[root@taoyuan ~]# mysql -uroot

注： -p=passwd，使用密码登录，在此可以将密码直接输入在命令行（跟在-p后面，不加空格：-p'123456'<此处单引号可以不加，但是当密码中有特殊符号时必须加，所以在命令行输入密码时养成习惯：加单引号>），也可以不在命令行输入，只跟-p选项，然后根据提示信息：“Enter password”，输入密码进行登录（此方法不会暴露用户密码，安全）。

设置mysql 的root密码 && 更改

[root@taoyuan ~]# mysqladmin -uroot password '123456'
Warning: Using a password on the command line interface can be insecure.

[root@taoyuan ~]# mysql -uroot -p
Enter password:
#输入密码

#更改新的密码
[root@taoyuan ~]# mysqladmin -uroot -p'123456' password 'taoyuan'
Warning: Using a password on the command line interface can be insecure.
[root@taoyuan ~]# mysql -uroot -p'taoyuan'
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.

密码重置

[root@taoyuan ~]# vi /etc/my.cnf

#my.cnf 配置文件内容
[mysqld]
skip-grant
datadir=/data/mysql #增加skip-grant
#忽略授权，意思是不用密码登陆

#重启mysql服务
[root@taoyuan ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!

#登陆mysql 修改一个表
mysql> use mysql;  #切换表
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> select * from user;

#查看user表
mysql> select password from user;
+-------------------------------------------+
| password                                  |
+-------------------------------------------+
| *758ABA8398EF87C993D2C4420DACD8946907C873 |
|                                           |
|                                           |
|                                           |
|                                           |
|                                           |
+-------------------------------------------+
6 rows in set (0.00 sec)

#修改密码
mysql> update user set password=password('Aa123456') where user='root';
Query OK, 4 rows affected (0.00 sec)
Rows matched: 4  Changed: 4  Warnings: 0

#quit ，把/etc/my.cnf 配置文件修改回去 ，重启mysql服务
[root@taoyuan ~]# vi /etc/my.cnf
[root@taoyuan ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!
[root@taoyuan ~]# mysql -uroot -p'Aa123456'
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.

注： 完成该操作之后就可以任意登录mysql了（无需密码），所以此时mysql安全性很差，平时配置文件中一定不要添加该参数！！

13.2 连接mysql

本机直接登陆

[root@taoyuan ~]# mysql -uroot -pAa123456

通过端口连接（TCP/IP）

[root@taoyuan ~]# mysql -uroot -pAa123456 -h127.0.0.1 -P3306
# -P 指定端口

使用sock的连接

[root@taoyuan ~]# mysql -uroot -pAa123456 -S/tmp/mysql.sock
#适用于本机连接

连接mysql操作一个命令

[root@taoyuan ~]# mysql -uroot -pAa123456 -e "show databases"
Warning: Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
#shell脚本使用中比较方便，可以直接获取数据

13.3 mysql常用命令

#查询库
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.00 sec)

#切换库
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

#查看库里的表
mysql> show tables;

#查看字段
mysql> desc user;

#查看建表语句
mysql> show create table user\G;
#\G 表示：竖排显示

#查看当前用户
mysql> select user();
+----------------+
| user()         |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)

#查看当前使用的数据库
mysql> select database();
+------------+
| database() |
+------------+
| NULL       |
+------------+
1 row in set (0.00 sec)

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
mysql> select database();
+------------+
| database() |
+------------+
| mysql      |
+------------+
1 row in set (0.00 sec)

#创建库
mysql> create database db1;
Query OK, 1 row affected (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

#创建表
mysql> use db1;
Database changed
mysql> create table t1(`id` int(4), `name` char(40));
Query OK, 0 rows affected (0.02 sec)

mysql> show create table t1\G;
*************************** 1. row ***************************
Table: t1
Create Table: CREATE TABLE `t1` (
`id` int(4) DEFAULT NULL,
`name` char(40) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

ERROR:
No query specified
#ENGINE=InnoDB DEFAULT CHARSET=latin1 可以自定义
#如下
mysql> drop table t1; #删除t1表
Query OK, 0 rows affected (0.01 sec)
mysql> create table t1(`id` int(4), `name` char(40)) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.01 sec)

mysql> show create table t1\G;
*************************** 1. row ***************************
Table: t1
Create Table: CREATE TABLE `t1` (
`id` int(4) DEFAULT NULL,
`name` char(40) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

ERROR:
No query specified

#查看当前数据库版本
mysql> select version();
+-----------+
| version() |
+-----------+
| 5.6.35    |
+-----------+
1 row in set (0.00 sec)

#查看数据库状态
mysql> show status;

#查看各参数
mysql> show variables
#指定的参数
mysql> show variables like 'max_connect%';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| max_connect_errors | 100   |
| max_connections    | 151   |
+--------------------+-------+
2 rows in set (0.00 sec)

#修改参数
mysql> set global max_connect_errors=1000;
Query OK, 0 rows affected (0.00 sec)
#只在内存中生效

#查看队列
mysql> show processlist;
+----+------+-----------+------+---------+------+-------+------------------+
| Id | User | Host      | db   | Command | Time | State | Info             |
+----+------+-----------+------+---------+------+-------+------------------+
|  9 | root | localhost | db1  | Query   |    0 | init  | show processlist |
+----+------+-----------+------+---------+------+-------+------------------+
1 row in set (0.00 sec)

mysql> show full processlist;
+----+------+-----------+------+---------+------+-------+-----------------------+
| Id | User | Host      | db   | Command | Time | State | Info                  |
+----+------+-----------+------+---------+------+-------+-----------------------+
|  9 | root | localhost | db1  | Query   |    0 | init  | show full processlist |
+----+------+-----------+------+---------+------+-------+-----------------------+
1 row in set (0.00 sec)
#full 查看完整的队列

小常识：
敲过的命令历史在mysql_history 文件里