构建Mysql服务器
《综合》构建Mysql服务器
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)
4 表结构的调整
4.1 问题
本案例要求熟悉MySQL库中表的字段修改,主要练习以下操作:
- 添加字段
- 修改字段名
- 修改字段类型
- 删除字段
4.2 步骤
实现此案例需要按照如下步骤进行。
步骤一:添加字段
在home中创建tea6表
- mysql> CREATE TABLE home.tea6(id int(4) PRIMARY KEY,
- -> name varchar(4) NOT NULL,
- -> age int(2) NOT NULL
- -> );
- Query OK, 0 rows affected (0.34 sec)
为tea6表添加一个address字段
添加前:
- mysql> DESC tea6;
- +-------+------------+------+-----+---------+-------+
- | Field | Type | Null | Key | Default | Extra |
- +-------+------------+------+-----+---------+-------+
- | id | int(4) | NO | PRI | NULL | |
- | name | varchar(4) | NO | | NULL | |
- | age | int(2) | NO | | NULL | |
- +-------+------------+------+-----+---------+-------+
- 3 rows in set (0.00 sec)
添加address字段:
- mysql> ALTER TABLE tea6 ADD address varchar(48);
- Query OK, 0 rows affected (0.84 sec)
- Records: 0 Duplicates: 0 Warnings: 0
添加后(默认作为最后一个字段):
- mysql> DESC tea6;
- +---------+-------------+------+-----+---------+-------+
- | Field | Type | Null | Key | Default | Extra |
- +---------+-------------+------+-----+---------+-------+
- | id | int(4) | NO | PRI | NULL | |
- | name | varchar(4) | NO | | NULL | |
- | age | int(2) | NO | | NULL | |
- | address | varchar(48) | YES | | NULL | |
- +---------+-------------+------+-----+---------+-------+
- 4 rows in set (0.00 sec)
3)在tea6表的age列之后添加一个gender字段
添加操作:
- mysql> ALTER TABLE tea6 ADD gender enum('boy','girl') AFTER age;
- Query OK, 0 rows affected (0.59 sec)
- Records: 0 Duplicates: 0 Warnings: 0
确认添加结果:
- mysql> DESC tea6;
- +---------+--------------------+------+-----+---------+-------+
- | Field | Type | Null | Key | Default | Extra |
- +---------+--------------------+------+-----+---------+-------+
- | id | int(4) | NO | PRI | NULL | |
- | name | varchar(4) | NO | | NULL | |
- | age | int(2) | NO | | NULL | |
- | gender | enum('boy','girl') | YES | | NULL | |
- | address | varchar(48) | YES | | NULL | |
- +---------+--------------------+------+-----+---------+-------+
- 5 rows in set (0.00 sec)
步骤二:修改字段名和字段类型
将tea6表的gender字段改名为sex,并添加非空约束
修改操作:
- mysql> ALTER TABLE tea6 CHANGE gender
- -> sex enum('boy','girl') NOT NULL;
- Query OK, 0 rows affected (0.08 sec)
- Records: 0 Duplicates: 0 Warnings: 0
确认修改结果:
- mysql> DESC tea6;
- +---------+--------------------+------+-----+---------+-------+
- | Field | Type | Null | Key | Default | Extra |
- +---------+--------------------+------+-----+---------+-------+
- | id | int(4) | NO | PRI | NULL | |
- | name | varchar(4) | NO | | NULL | |
- | age | int(2) | NO | | NULL | |
- | sex | enum('boy','girl') | NO | | NULL | |
- | address | varchar(48) | YES | | NULL | |
- +---------+--------------------+------+-----+---------+-------+
- 5 rows in set (0.00 sec)
步骤三:删除字段
删除tea6表中名为sex的字段:
- mysql> ALTER TABLE tea6 DROP sex; //删除操作
- Query OK, 0 rows affected (0.52 sec)
- Records: 0 Duplicates: 0 Warnings: 0
- mysql> DESC tea6; //确认删除结果
- +---------+-------------+------+-----+---------+-------+
- | Field | Type | Null | Key | Default | Extra |
- +---------+-------------+------+-----+---------+-------+
- | id | int(4) | NO | PRI | NULL | |
- | name | varchar(4) | NO | | NULL | |
- | age | int(2) | NO | | NULL | |
- | address | varchar(48) | YES | | NULL | |
- +---------+-------------+------+-----+---------+-------+
- 4 rows in set (0.00 sec)