NSD DATABASE DAY01
1 构建MySQL服务器
1.1 问题
本案例要求熟悉MySQL官方安装包的使用，快速构建一台数据库服务器：
- 安装MySQL-server、MySQl-client软件包
- 修改数据库用户root的密码
- 确认MySQL服务程序运行、root可控
1.2 方案
本课程将使用64位的RHEL 7操作系统，MySQL数据库的版本是5.7.17。
访问http://dev.mysql.com/downloads/mysql/，找到MySQL Community Server下载页面，平台选择“Red Hat Enterprise Linux 7 / Oracle Linux”，然后选择64位的bundle整合包下载，如图-1所示。
图-1
注意：下载MySQL软件时需要以Oracle网站账户登录，如果没有请根据页面提示先注册一个（免费） 。
1.3 步骤
实现此案例需要按照如下步骤进行。
步骤一：准备工作
1）卸载系统自带的mariadb-server、mariadb软件包（如果有的话）
[root@dbsvr1 ~]# yum -y remove mariadb-server mariadb Setting up Remove Process No Match for argument: mariadb-server rhel7dvd | 3.9 kB 00:00 ... Package(s) mariadb-server available, but not installed. No Match for argument: mariadb Package(s) mariadb available, but not installed. No Packages marked for removal
2）清理/etc/my.cnf配置文件
此配置文件由RHEL自带的mariadb-libs库提供：
[root@dbsvr1 ~]# rpm -qf /etc/my.cnf mariadb-libs-5.5.35-3.el7.x86_64
大量的系统软件包都需要用到mariadb-libs库，因此不建议直接卸载此软件包。最好是安装新的MySQL数据库软件时，采用 -U 升级的方式来进行替换。
配置文件/etc/my.cnf若不需要使用，可以直接删除。或者保险起见，也可以将其改名备份：
[root@dbsvr1 ~]# mv /etc/my.cnf /etc/my.cnf.old
步骤二：安装mysql-community-client、mysql-community-server软件包
1）释放bundle整合包
[root@dbsvr1 ~]# cd /var/ftp/pub/ [root@dbsvr1 pub]# tar xvf mysql-5.7.17-1.el7.x86_64.rpm-bundle.tar mysql-community-client-5.7.17-1.el7.x86_64.rpm //MySQL 数据库客户端应用程序和工具 mysql-community-common-5.7.17-1.el7.x86_64.rpm //MySQL 数据库和客户端库共享文件 mysql-community-devel-5.7.17-1.el7.x86_64.rpm //MySQL 数据库客户端应用程序的库和头文件 mysql-community-embedded-5.7.17-1.el7.x86_64.rpm //MySQL嵌入式函数库 mysql-community-embedded-compat-5.7.17-1.el7.x86_64.rpm //MySQL嵌入式兼容函数库 mysql-community-embedded-devel-5.7.17-1.el7.x86_64.rpm //头文件和库文件作为Mysql的嵌入式库文件 mysql-community-libs-5.7.17-1.el7.x86_64.rpm //MySQL 数据库客户端应用程序的共享库 mysql-community-libs-compat-5.7.17-1.el7.x86_64.rpm //MySQL 5.6.31 数据库客户端应用程序的共享兼容库 mysql-community-minimal-debuginfo-5.7.17-1.el7.x86_64.rpm //mysql最小安装包的调试信息 mysql-community-server-5.7.17-1.el7.x86_64.rpm //非常快速和可靠的 SQL 数据库服务器 mysql-community-server-minimal-5.7.17-1.el7.x86_64.rpm //非常快速和可靠的 SQL 数据库服务器(最小化安装) mysql-community-test-5.7.17-1.el7.x86_64.rpm //MySQL 数据库服务器的测试套件
2）安装MySQL数据库
在bundle的整合包中，并不是所有的rpm包都会用到，将一些重复的删除。
安装mysql时可能会缺少某些依赖包，需提前单独安装
[root@dbsvr1 pub]#yum -y install perl-Data-Dumper perl-JSON perl-Time-HiRes [root@dbsvr1 pub]# rpm -Uvh mysql-community-*.rpm 准备中... ################################# [100%] 正在升级/安装... 1:mysql-community-common-5.7.17-1.e################################# [ 9%] 2:mysql-community-libs-5.7.17-1.el7################################# [ 18%] 3:mysql-community-client-5.7.17-1.e################################# [ 27%] 4:mysql-community-server-5.7.17-1.e################################# [ 36%] 5:mysql-community-devel-5.7.17-1.el################################# [ 45%] 6:mysql-community-embedded-5.7.17-1################################# [ 55%] 7:mysql-community-embedded-devel-5.################################# [ 64%] 8:mysql-community-test-5.7.17-1.el7################################# [ 73%] 9:mysql-community-libs-compat-5.7.1################################# [ 82%] 10:mysql-community-minimal-debuginfo################################# [ 91%] 正在清理/删除... 11:mariadb-libs-1:5.5.35-3.el7 ################################# [100%] [root@dbsvr1 pub]#systemctl start mysqld.service
安装过程中会尝试做一些检测，然后完成基本的初始化任务，期间会给出相关的提示。比如由于MySQL 5.7对TIMESTAMP时间戳的处理不同于之前的版本，会给出警告和提示出解决办法（使用--explicit_defaults_for_timestamp选项）：
2017-04-04T15:59:07.324470Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
MySQL 5.7默认采用的存储引擎不再是MyISAM，而是InnoDB。初始化时若相关的文件不存在，会自动创建并设置相关参数：
2017-04-04T15:59:09.075698Z 0 [Warning] InnoDB: New log files created, LSN=45790
2017-04-04T15:59:09.381634Z 0 [Warning] InnoDB: Creating foreign key constraint system tables.
2017-04-04T15:59:09.579733Z 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: a3973917-194f-11e7-a75b-52540018542e.
2017-04-04T15:59:09.703759Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.
2017-04-04T15:59:09.711439Z 1 [Note] A temporary password is generated for root@localhost: ;%7SDdD)quOI
2017-04-04T15:59:29.758102Z 1 [ERROR] Failed to open the bootstrap file /tmp/install-validate-password-plugin.xqy7Ay.sql
2017-04-04T15:59:29.758122Z 1 [ERROR] 1105 Bootstrap file error, return code (0). Nearest query: 'LSE SET @sys.tmp.table_exists.SQL = CONCAT('SELECT COUNT(*) FROM `', in_db, '`.`', in_table, '`'); PREPARE stmt_select FROM @sys.tmp.table_exists.SQL; IF (NOT v_error) THEN DEALLOCATE PREPARE stmt_select; SET out_exists = 'TEMPORARY'; END IF; END IF; END;
'
2017-04-04T15:59:29.758336Z 0 [ERROR] Aborting
2017-04-04T15:59:33.078575Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2017-04-04T15:59:33.092082Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.17) starting as process 3326 ...
2017-04-04T15:59:33.095074Z 0 [Note] InnoDB: PUNCH HOLE support available
2017-04-04T15:59:33.095104Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2017-04-04T15:59:33.095109Z 0 [Note] InnoDB: Uses event mutexes
2017-04-04T15:59:33.095112Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2017-04-04T15:59:33.095115Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.3
2017-04-04T15:59:33.095120Z 0 [Note] InnoDB: Using Linux native AIO
2017-04-04T15:59:33.095340Z 0 [Note] InnoDB: Number of pools: 1
2017-04-04T15:59:33.095428Z 0 [Note] InnoDB: Not using CPU crc32 instructions
2017-04-04T15:59:33.096904Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2017-04-04T15:59:33.106888Z 0 [Note] InnoDB: Completed initialization of buffer pool
2017-04-04T15:59:33.108711Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2017-04-04T15:59:33.120189Z 0 [Note] InnoDB: Highest supported file format is Barracuda.
2017-04-04T15:59:33.454908Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
2017-04-04T15:59:33.455034Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2017-04-04T15:59:34.057704Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2017-04-04T15:59:34.058603Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2017-04-04T15:59:34.058615Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2017-04-04T15:59:34.063078Z 0 [Note] InnoDB: Waiting for purge to start
2017-04-04T15:59:34.113304Z 0 [Note] InnoDB: 5.7.17 started; log sequence number 2536157
2017-04-04T15:59:34.113841Z 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool
2017-04-04T15:59:34.114310Z 0 [Note] Plugin 'FEDERATED' is disabled.
2017-04-04T15:59:34.118690Z 0 [Note] Found ca.pem, server-cert.pem and server-key.pem in data directory. Trying to enable SSL support using them.
2017-04-04T15:59:34.118921Z 0 [Warning] CA certificate ca.pem is self signed.
2017-04-04T15:59:34.119582Z 0 [Note] InnoDB: Buffer pool(s) load completed at 170404 23:59:34
2017-04-04T15:59:34.237643Z 0 [Note] Server hostname (bind-address): '*'; port: 3306
2017-04-04T15:59:34.241687Z 0 [Note] IPv6 is available.
2017-04-04T15:59:34.241727Z 0 [Note] - '::' resolves to '::';
2017-04-04T15:59:34.241753Z 0 [Note] Server socket created on IP: '::'.
2017-04-04T15:59:34.313591Z 0 [Note] Event Scheduler: Loaded 0 events
2017-04-04T15:59:34.313686Z 0 [Note] Executing 'SELECT * FROM INFORMATION_SCHEMA.TABLES;' to get a list of tables using the deprecated partition engine. You may use the startup option '--disable-partition-engine-check' to skip this check.
2017-04-04T15:59:34.313693Z 0 [Note] Beginning of list of non-natively partitioned tables
2017-04-04T15:59:34.322126Z 0 [Note] End of list of non-natively partitioned tables
2017-04-04T15:59:34.322261Z 0 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.7.17' socket: '/var/lib/mysql/mysql.sock' port: 3306 MySQL Community Server (GPL)
关于MySQL数据库的管理员账号root，其密码也不再是空，而是安装时随机生成一个，这种处理方式一定程度上增强了MySQl服务器的安全性。随机生成的密码字串可以从保存到mysql日志文件中找到：
[root@dbsvr1 pub]#grep 'temporary password' /var/log/mysqld.log 2017-04-04T15:59:09.711439Z 1 [Note] A temporary password is generated for root@localhost: ;%7SDdD)quOI
3）确认安装后的服务单元文件、服务状态
查看服务单元文件
[root@dbsvr1 pub]# ls -lh /usr/lib/systemd/system/mysqld.service -rw-r--r--. 1 root root 1.6K 11月 29 04:30 /usr/lib/systemd/system/mysqld.service
mysql服务的自启状态为enabled：
[root@dbsvr1 ~]# # systemctl is-enabled mysqld.service enabled
步骤三：查看Mysql服务的运行状态
服务器进程为mysqld，监听的默认端口为TCP 3306：
[root@dbsvr1 pub]# netstat -antpu | grep mysql tcp6 0 0 :::3306 :::* LISTEN 3913/mysqld
查看Mysql服务的状态
[root@dbsvr1 pub]#systemctl is-active mysqld.service
active
[root@dbsvr1 pub]#systemctl status mysqld.service
mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled)
Active: active (running) since 日 2017-04-23 08:56:24 CST; 1s ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 13753 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Process: 13732 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 13757 (mysqld)
CGroup: /system.slice/mysqld.service
└─13757 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
数据库的默认存放位置为 /var/lib/mysql：
[root@dbsvr1 pub]# ls /var/lib/mysql auto.cnf client-cert.pem ibdata1 ibtmp1 mysql.sock.lock public_key.pem sys ca-key.pem client-key.pem ib_logfile0 mysql performance_schema server-cert.pem ca.pem ib_buffer_pool ib_logfile1 mysql.sock private_key.pem server-key.pem
步骤四：连接MySQL服务器，修改密码
查看随机生成的root管理密码
[root@dbsvr1 pub]#grep 'temporary password' /var/log/mysqld.log 2017-04-01T18:10:42.948679Z 1 [Note] A temporary password is generated for root@localhost: GWphBZ_g+1& //密码为GWphBZ_g+1&
2）使用客户端命令mysql连接到MySQL服务器
提示验证时，填入前一步获得的随机密码，验证成功后即可进入“mysql> ”环境：
[root@dbsvr1 pub]# mysql -u root -p Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 14 Server version: 5.7.17 Copyright (c) 2000, 2016, 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> //登录成功后，进入SQL操作环境
用该密码登录到服务端后，必须马上修改密码，不然会报如下错误：
mysql> show databases; ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
3）执行SET PASSWORD命令修改密码
这个其实与validate_password_policy的值有关，默认为1，所以刚开始设置的密码必须符合长度，且必须含有数字，小写或大写字母，特殊字符。如果我们不希望密码设置的那么复杂，需要修改两个全局参数：validate_password_policy与validate_password_length。validate_password_length默认值为8,最小值为4，如果你显性指定validate_password_length的值小于4，尽管不会报错，但validate_password_length的值将设为4。
可参考下列指令：
mysql>set global validate_password_policy=0;
mysql>set global validate_password_length=4；
mysql> SET PASSWORD FOR 'root'@'localhost'=PASSWORD('1234567');
Query OK, 0 rows affected, 1 warning (0.00 sec)
上述操作的结果是——更改数据库用户root从本机访问时的密码，设为1234567。
退出“mysql> ”环境，重新登录验证，必须采用新的密码才能登入：
mysql> exit //退出 mysql> 环境 Bye [root@dbsvr1 ~]# mysql -u root –p //重新登录 Enter password: //输入新设置的密码 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 15 Server version: 5.7.17 MySQL Community Server (GPL) Copyright (c) 2000, 2016, 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> mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.07 sec)
2 数据库基本管理
2.1 问题
本案例要求熟悉MySQL的连接及数据库表的增删改查等基本管理操作，主要完成以下几个方便的操作：
- 使用mysql命令连接数据库
- 练习查看/删除/创建库的相关操作
- 练习查看/删除/创建表的相关操作，表数据参考如表-1所示内容
表－1 测试用表数据
2.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：使用mysql命令连接数据库
连接MySQL服务器时，最基本的用法是通过 -u 选项指定用户名、-p指定密码。密码可以写在命令行（如果不写，则出现交互，要求用户输入），当然基于安全考虑一般不推荐这么做：
[root@dbsvr1 ~]# mysql -uroot -p123456 //紧挨着选项，不要空格 mysql: [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 16 Server version: 5.7.17 MySQL Community Server (GPL) Copyright (c) 2000, 2016, 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 //退出已登录的mysql> 环境 Bye
默认情况下，msyql命令会连接本机的MySQL服务。但在需要的时候，可以通过 -h 选项指定远程主机；如果端口不是3306，还可以通过大写的 -P 选项指定：
[root@dbsvr1 ~]# mysql -u root -p -h 127.0.0.1 -P 3306 Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 17 Server version: 5.7.17 MySQL Community Server (GPL) Copyright (c) 2000, 2016, 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 //退出已登录的mysql> 环境 Bye
连接其他主机的MySQL服务，有一个前提条件——对方已经添加了此用户从此客户机访问的数据库授权，授权操作方法会在后续课程学习。
步骤二：练习查看/删除/创建库的相关操作
以root用户登入“mysql> ”环境后，可以执行各种MySQL指令、SQL指令。基本的用法事项如下：
- 操作指令不区分大小写（库名/表名、密码、变量值等除外）。
- 每条SQL指令以 ; 结束或分隔。
- 不支持 Tab 键自动补齐。
- \c 可废弃当前编写错的操作指令。
1）查看现有的库
mysql> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | //信息概要库 | mysql | //授权库 | performance_schema | //性能结构库 | sys | //系统元数据库 +--------------------+ 4 rows in set (0.15 sec)
2）切换/使用指定的库
切换到sys库：
mysql> USE sys; Database changed mysql> SELECT DATABASE(); //确认当前所在的库 +------------+ | DATABASE() | +------------+ | sys | +------------+ 1 row in set (0.00 sec)
切换到mysql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 mysql> SELECT DATABASE(); //确认当前所在的库 +------------+ | DATABASE() | +------------+ | mysql | +------------+ 1 row in set (0.00 sec)
3）创建新的库
新建名为mydb的库，确认结果：
mysql> CREATE DATABASE mydb; Query OK, 1 row affected (0.00 sec) mysql> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | mydb | //新建的mydb库 | mysql | | performance_schema | | sys | +--------------------+ 5 rows in set (0.00 sec)
新建名为newdb的库，确认结果：
mysql> CREATE DATABASE newdb; Query OK, 1 row affected (0.00 sec) mysql> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | mydb | //新建的mydb库 | mysql | | newdb | //新建的newdb库 | performance_schema | | sys | +--------------------+ 6 rows in set (0.00 sec)
新建数据库以后，会为每个数据库建立同名文件夹，可从命令行确认：
[root@dbsvr1 ~]# ls -l /var/lib/mysql/{my,new}db/
/var/lib/mysql/mydb/:
总用量 4
-rw-r-----. 1 mysql mysql 65 4月 2 03:14 db.opt
/var/lib/mysql/newdb/:
总用量 4
-rw-r-----. 1 mysql mysql 65 4月 2 03:15 db.opt
4）删除指定的库
删除名为newdb的库：
mysql> DROP DATABASE newdb; Query OK, 0 rows affected (0.04 sec) mysql> SHOW DATABASES; //确认删除结果，已无newdb表 +--------------------+ | Database | +--------------------+ | information_schema | | mydb | | mysql | | performance_schema | | sys | +--------------------+ 5 rows in set (0.00 sec)
步骤三：练习查看/删除/创建表的相关操作
1）查看指定的库里有哪些表
查看mysql库里有哪些表：
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 | | engine_cost | | event | | func | | general_log | | gtid_executed | | help_category | | help_keyword | | help_relation | | help_topic | | innodb_index_stats | | innodb_table_stats | | ndb_binlog_index | | plugin | | proc | | procs_priv | | proxies_priv | | server_cost | | 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 | //存放数据库用户的表 +---------------------------+ 31 rows in set (0.00 sec)
2）查看指定表的字段结构
当前库为mysql，查看columns_priv表的结构，以列表形式展现：
mysql> DESCRIBE columns_priv\G //末尾不用分号
*************************** 1. row ***************************
Field: Host
Type: char(60)
Null: NO
Key: PRI
Default:
Extra:
*************************** 2. row ***************************
Field: Db
Type: char(64)
Null: NO
Key: PRI
Default:
Extra:
*************************** 3. row ***************************
Field: User
Type: char(32)
Null: NO
Key: PRI
Default:
Extra:
*************************** 4. row ***************************
Field: Table_name
Type: char(64)
Null: NO
Key: PRI
Default:
Extra:
*************************** 5. row ***************************
Field: Column_name
Type: char(64)
Null: NO
Key: PRI
Default:
Extra:
*************************** 6. row ***************************
Field: Timestamp
Type: timestamp
Null: NO
Key:
Default: CURRENT_TIMESTAMP
Extra: on update CURRENT_TIMESTAMP
*************************** 7. row ***************************
Field: Column_priv
Type: set('Select','Insert','Update','References')
Null: NO
Key:
Default:
Extra:
7 rows in set (0.01 sec)
查看columns_priv表的结构，以表格形式展现：
mysql> DESCRIBE columns_priv; //末尾需要有分号
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Host | char(60) | NO | PRI | | |
| Db | char(64) | NO | PRI | | |
| User | char(32) | NO | PRI | | |
| Table_name | char(64) | NO | PRI | | |
| Column_name | char(64) | NO | PRI | | |
| Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| Column_priv | set('Select','Insert','Update','References') | NO | | | |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
7 rows in set (0.00 sec)
上述操作中，DESCRIBE可缩写为DESC；另外，当引用非当前库中的表时，可以用“库名.表名”的形式。比如，切换为mysql库再执行“DESCRIBE columns_priv;”，与以下操作的效果是相同的：
mysql> DESC mysql.columns_priv;
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
| Host | char(60) | NO | PRI | | |
| Db | char(64) | NO | PRI | | |
| User | char(16) | NO | PRI | | |
| Table_name | char(64) | NO | PRI | | |
| Column_name | char(64) | NO | PRI | | |
| Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| Column_priv | set('Select','Insert','Update','References') | NO | | | |
+-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
7 rows in set (0.00 sec)
3）在test库中创建一个名为pwlist的表
包括name、password两列，其中name列作为主键。两个字段值均不允许为空，其中密码列赋予默认空值，相关操作如下所述。
切换到mydb库：
mysql> USE mydb; Database changed
新建pwlist表：
mysql> CREATE TABLE pwlist(
-> name CHAR(16) NOT NULL,
-> password CHAR(48) DEFAULT '',
-> PRIMARY KEY(name)
-> );
Query OK, 0 rows affected (0.38 sec)
确认新创建的表：
mysql> SHOW TABLES; +----------------+ | Tables_in_mydb | +----------------+ | pwlist | //新建的pwlist表 +----------------+ 1 rows in set (0.01 sec)
查看pwlist表的字段结构：
mysql> DESC pwlist; +----------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+----------+------+-----+---------+-------+ | name | char(16) | NO | PRI | NULL | | | password | char(48) | YES | | | | +----------+----------+------+-----+---------+-------+ 2 rows in set (0.01 sec)
4）删除指定的表
删除当前库中的pwlist表：
mysql> DROP TABLE pwlist; Query OK, 0 rows affected (0.01 sec)
确认删除结果：
mysql> SHOW TABLES; Empty set (0.00 sec)
5）在mydb库中创建一个学员表
表格结构及数据内容如表-1所示。
在MySQL表内存储中文数据时，需要更改字符集（默认为latin1不支持中文），以便MySQL支持存储中文数据记录；比如，可以在创建库或表的时候，手动添加“DEFAULT CHARSET=utf8”来更改字符集。
根据上述表格结构，创建支持中文的student表：
mysql> CREATE TABLE mydb.student(
-> 学号 char(9) NOT NULL,
-> 姓名 varchar(4) NOT NULL,
-> 性别 enum('男','女') NOT NULL,
-> 手机号 char(11) DEFAULT '',
-> 通信地址 varchar(64),
-> PRIMARY KEY(学号)
-> ) DEFAULT CHARSET=utf8; //手工指定字符集，采用utf8
Query OK, 0 rows affected (0.31sec)
查看student表的字段结构：
mysql> DESC mydb.student;
+--------------+-------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------------+------+-----+---------+-------+
| 学号 | char(9) | NO | PRI | NULL | |
| 姓名 | varchar(4) | NO | | NULL | |
| 性别 | enum('男','女') | NO | | NULL | |
| 手机号 | char(11) | YES | | | |
| 通信地址 | varchar(64) | YES | | NULL | |
+--------------+-------------------+------+-----+---------+-------+
5 rows in set (0.04 sec)
查看student表的实际创建指令：
mysql> SHOW CREATE TABLE mydb.student;
+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| student | CREATE TABLE `student` (
`学号` char(9) NOT NULL,
`姓名` varchar(4) NOT NULL,
`性别` enum('男','女') NOT NULL,
`手机号` char(11) DEFAULT '',
`通信地址` varchar(64) DEFAULT NULL,
PRIMARY KEY (`学号`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
注意：若要修改MySQL服务的默认字符集，可以更改服务器的my.cnf配置文件，添加character_set_server=utf8 配置，然后重启数据库服务。
[root@dbsvr1 ~]# vim /etc/my.cnf //修改运行服务配置 [mysqld] .. .. character_set_server=utf8 [root@dbsvr1 ~]# systemctl restart mysqld //重启服务 .. .. [root@dbsvr1 ~]# mysql –u root -p Enter password: .. .. mysql> SHOW VARIABLES LIKE 'character%'; //确认更改结果 +--------------------------+----------------------------+ | Variable_name | Value | +--------------------------+----------------------------+ | character_set_client | utf8 | | character_set_connection | utf8 | | character_set_database | utf8 | | character_set_filesystem | binary | | character_set_results | utf8 | | character_set_server | utf8 | | character_set_system | utf8 | | character_sets_dir | /usr/share/mysql/charsets/ | +--------------------------+----------------------------+ 8 rows in set (0.03 sec)
3 MySQL 数据类型
3.1 问题
本案例要求熟悉MySQL的字段数据类型、时间函数的使用，完成以下任务操作：
- 在home库里创建famliy表，表结构、字段类型自定义
- 练习各种时间函数的使用
3.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：创建home库、family表
1）新建home库，并切换到home库
mysql> CREATE DATABASE home; Query OK, 1 row affected (0.00 sec) mysql> USE home; Database changed
2）新建family表
假定family表用来记录每个家庭成员的姓名（name）、性别（gender）、出生日期（birth）、职业（job）、与户主关系（relation）。
mysql> CREATE TABLE family(
-> name varchar(16) NOT NULL,
-> gender enum('male','femal') DEFAULT 'male',
-> birth date NOT NULL,
-> job varchar(16) DEFAULT '',
-> relation varchar(24) NOT NULL,
-> PRIMARY KEY(name)
-> );
Query OK, 0 rows affected (0.61sec)
查看family表的字段结构：
mysql> DESC family;
+----------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+-------+
| name | varchar(16) | NO | PRI | NULL | |
| gender | enum('male','femal') | YES | | male | |
| birth | date | NO | | NULL | |
| job | varchar(16) | YES | | | |
| relation | varchar(24) | NO | | NULL | |
+----------+----------------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
步骤二：练习各种时间函数的使用
1）使用now()查看当前的日期和时间
mysql> SELECT now(); +---------------------+ | now() | +---------------------+ | 2017-04-02 04:02:42 | +---------------------+ 1 row in set (0.00 sec)
2）使用sysdate()查看系统日期和时间
mysql> SELECT sysdate(); +---------------------+ | sysdate() | +---------------------+ | 2017-04-02 04:03:21 | +---------------------+ 1 row in set (0.00 sec)
3）使用curdate()获得当前的日期，不含时间
mysql> SELECT curdate(); +------------+ | curdate() | +------------+ | 2017-04-02 | +------------+ 1 row in set (0.00 sec)
4）使用curtime()获得当前的时间，不含日期
mysql> SELECT curtime(); +-----------+ | curtime() | +-----------+ | 04:04:55 | +-----------+ 1 row in set (0.00 sec)
5）分别获取当前日期时间中的年份、月份、日
mysql> SELECT year(now()),month(now()),day(now()); +-------------+--------------+------------+ | year(now()) | month(now()) | day(now()) | +-------------+--------------+------------+ | 2017 | 4 | 2 | +-------------+--------------+------------+ 1 row in set (0.00 sec)
6）获取系统日期时间中的月份、日
mysql> SELECT month(sysdate()),day(sysdate()); +------------------+----------------+ | month(sysdate()) | day(sysdate()) | +------------------+----------------+ | 4 | 2 | +------------------+----------------+ 1 row in set (0.00 sec)
7）获取系统日期时间中的时刻
mysql> SELECT time(sysdate()); +-----------------+ | time(sysdate()) | +-----------------+ | 04:06:08 | +-----------------+ 1 row in set (0.00 sec)