设置MySQL数据库密码，链接数据库以及基本操做的经常使用命令

1、更改MySQL的root用户密码

一、首次进入数据库

[root@zlinux ~]# /usr/local/mysql/bin/mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> quit
Bye

首次进入数据库使用了绝对路径，直接使用mysql命令是不行的，由于/usr/local/mysql/bin/再也不PATH这个环境变量里。还有在首次进入数据库时，密码为空。退出时，输入quit或者exit便可。

二、把mysql命令绝对路径加入环境变量

[root@zlinux ~]# export PATH=$PATH:/usr/local/mysql/bin    //临时加入环境变量，重启就会失效
[root@zlinux ~]# echo "PATH=$PATH:/usr/local/mysql/bin" >> /etc/profile      //追加到profile文件中，使环境变量永久生效
[root@zlinux ~]# source /etc/profile     //从新加载配置
[root@zlinux ~]# mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

三、设置和更改root密码

[root@zlinux ~]# mysqladmin -uroot password '123456'                  //在实际生产环境中请勿设置如此简单的密码
Warning: Using a password on the command line interface can be insecure.
[root@zlinux ~]# mysqladmin -uroot password '123456'
Warning: Using a password on the command line interface can be insecure.
[root@zlinux ~]# mysql -uroot     //设置好密码以后，再次使用以前的登陆密令就报错了
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
[root@zlinux ~]# mysql -uroot -p123456     //输入密码后再登陆，-p选项后面直接跟密码，不能有空格
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> quit
Bye
[root@zlinux ~]# mysql -uroot -p     //-p后面不加密码，以交互的形式输入密码
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> exit
Bye
[root@zlinux ~]# mysqladmin -uroot -p123456 password 'zlinux'   //修改密码
Warning: Using a password on the command line interface can be insecure.
[root@zlinux ~]# mysql -uroot -pzlinux     //使用新密码登陆
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

四、忘记root密码时的操做

[root@zlinux ~]# vim /etc/my.cnf

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html
# *** DO NOT EDIT THIS FILE. It's a template which will be copied to the
# *** default location during install, and will be replaced if you
# *** upgrade to a newer version of MySQL.

[mysqld]
skip-grant                                     //在[mysqld]下加入该字段

[root@zlinux ~]# /etc/init.d/mysqld restart      //重启mysql
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS! 
[root@zlinux ~]# mysql -uroot              //如今就无需密码了
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use mysql;                        //切换数据库
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> update user set password=password('zlinux123456') where user='root';            //更新密码
Query OK, 4 rows affected (0.00 sec)
Rows matched: 4  Changed: 4  Warnings: 0

mysql> exit
Bye
[root@zlinux ~]# vim /etc/my.cnf    //删除skip-grant字段
[root@zlinux ~]# /etc/init.d/mysqld restart   //重启
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS! 
[root@zlinux ~]# mysql -uroot    //没法登录了
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
[root@zlinux ~]# mysql -uroot -pzlinux123456    //使用新密码登陆
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> exit
Bye

2、链接数据库

[root@zlinux ~]# mysql -uroot -p -h192.168.242.128 -P3306            //-P指定端口， -h指定ip进行登陆
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> exit
Bye
[root@zlinux ~]# mysql -uroot -p -S/tmp/mysql.sock    //使用sock登陆，只适用于本地链接，等同于“mysql -uroot -p123456”
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> exit
Bye

3、MySQL基本操做的经常使用命令

查询当前全部库：show databases;
切换库： use mysql;
查看库里的表： show tables;
查看表全部字段： desc tb_name; //tb_name表示字段名
查看建表语句： show create table tb_name\G; //\G表示由竖排显示（示的更加有条理）
查看当前用户： select user();
查看当前使用的数据库： select databsase();
建立库： create database db1;
建立表： use db1; create table t1(id int(4), name char(40));
查看当前数据库版本： select version();
查看数据库状态： show status;
查看各参数 ：show variables; show variables like 'max_connect%';
修改参数： set global max_connect_errors=1000;
查看队列：show processlist; show full processlist;

简单演示：

[root@zlinux ~]# mysql -uroot -p -S/tmp/mysql.sock
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.6.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.01 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> show tables;
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
| columns_priv              |
| db                        |
| event                     |
| func                      |
| general_log               |
| help_category             |
| help_keyword              |
| help_relation             |
| help_topic                |
| innodb_index_stats        |
| innodb_table_stats        |
| ndb_binlog_index          |
| plugin                    |
| proc                      |
| procs_priv                |
| proxies_priv              |
| servers                   |
| slave_master_info         |
| slave_relay_log_info      |
| slave_worker_info         |
| slow_log                  |
| tables_priv               |
| time_zone                 |
| time_zone_leap_second     |
| time_zone_name            |
| time_zone_transition      |
| time_zone_transition_type |
| user                      |
+---------------------------+
28 rows in set (0.00 sec)

mysql> desc func;
+-------+------------------------------+------+-----+---------+-------+
| Field | Type                         | Null | Key | Default | Extra |
+-------+------------------------------+------+-----+---------+-------+
| name  | char(64)                     | NO   | PRI |         |       |
| ret   | tinyint(1)                   | NO   |     | 0       |       |
| dl    | char(128)                    | NO   |     |         |       |
| type  | enum('function','aggregate') | NO   |     | NULL    |       |
+-------+------------------------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

mysql> select user();
+----------------+
| user()         |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)

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

mysql>