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NSD DBA1 DAY01

  1. 构建MySQL服务器
  2. 数据库基本管理
  3. MySQL 数据类型

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:

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)停止mariadb服务

  1. [root@localhost ~]# systemctl stop mariadb

2)删除/etc/my.cnf配置文件

此配置文件由RHEL自带的mariadb-libs库提供:

[root@localhost ~]# rm -rf /etc/my.cnf

3)删除数据

  1. [root@localhost ~]# rm -rf /var/lib/mysql/*

4)卸载软件包(没有会显示未安装软件包)

  1. [root@localhost ~]# rpm -e --nodeps mariadb-server mariadb
  2. 警告:/var/log/mariadb/mariadb.log 已另存为/var/log/mariadb/mariadb.log.rpmsave

步骤二:安装软件包

1)安装mysql时可能会缺少某些依赖包,需提前单独安装

  1. [root@localhost ~]# yum -y install perl-Data-Dumper perl-JSON perl-Time-HiRes

2)物理机传输解压包给虚拟机192.168.4.1

  1. [root@room9pc01 ~]# cd 桌面
  2. [root@room9pc01 桌面]# scp mysql-5.7.17.tar 192.168.4.1:/root/ //给虚拟机传包
  3. root@192.168.4.1's password:
  4. mysql-5.7.17.tar 100% 543MB 95.6MB/s 00:05

3)虚拟机192.168.4.1解压mysql-5.7.17.tar 整合包

  1. [root@localhost ~]# tar -xvf mysql-5.7.17.tar //解压mysql整合包
  2. ./mysql-community-client-5.7.17-1.el7.x86_64.rpm
  3. ./mysql-community-common-5.7.17-1.el7.x86_64.rpm
  4. ./mysql-community-devel-5.7.17-1.el7.x86_64.rpm
  5. ./mysql-community-embedded-5.7.17-1.el7.x86_64.rpm
  6. ./mysql-community-embedded-compat-5.7.17-1.el7.x86_64.rpm
  7. ./mysql-community-embedded-devel-5.7.17-1.el7.x86_64.rpm
  8. ./mysql-community-libs-5.7.17-1.el7.x86_64.rpm
  9. ./mysql-community-libs-compat-5.7.17-1.el7.x86_64.rpm
  10. ./mysql-community-minimal-debuginfo-5.7.17-1.el7.x86_64.rpm
  11. ./mysql-community-server-5.7.17-1.el7.x86_64.rpm
  12. ./mysql-community-test-5.7.17-1.el7.x86_64.rpm

步骤三:启动MySQL数据库服务并设置开机自启

  1. [root@localhost ~]# systemctl start mysqld //启动mysql服务
  2. [root@localhost ~]# systemctl enable mysqld //设置开机自启
  3. [root@localhost ~]# systemctl status mysqld //查看mysql服务状态
  4. ● mysqld.service - MySQL Server
  5. Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
  6. Active: active (running) since 二 2018-08-28 10:03:24 CST; 8min ago
  7. Docs: man:mysqld(8)
  8. http://dev.mysql.com/doc/refman/en/using-systemd.html
  9. Main PID: 4284 (mysqld)
  10. CGroup: /system.slice/mysqld.service
  11. └─4284 /usr/sbin/mysqld --daemonize --pid-file=/var/r...
  12.  
  13. 828 10:02:56 localhost.localdomain systemd[1]: Starting MySQ...
  14. 828 10:03:24 localhost.localdomain systemd[1]: Started MySQL...
  15. Hint: Some lines were ellipsized, use -l to show in full.

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

  1. [root@localhost ~]#grep 'temporary password' /var/log/mysqld.log
  2. 2017-04-01T18:10:42.948679Z 1 [Note] A temporary password is generated for root@localhost: mtoa>Av<p6Yk //随机生成的管理密码为mtoa>Av<p6Yk

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:

  1. [root@localhost ~]# mysql -u root -p'mtoa>Av<p6Yk'
  2. mysql: [Warning] Using a password on the command line interface can be insecure.
  3. Welcome to the MySQL monitor. Commands end with ; or \g.
  4. Your MySQL connection id is 11
  5. Server version: 5.7.17
  6.  
  7. Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  8.  
  9. Oracle is a registered trademark of Oracle Corporation and/or its
  10. affiliates. Other names may be trademarks of their respective
  11. owners.
  12.  
  13. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  14. 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:

  1. mysql> show databases;
  2. 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:

  1. mysql>set global validate_password_policy=0; //只验证长度
  2. Query OK, 0 rows affected (0.00 sec)
  3. mysql>set global validate_password_length=6//修改密码长度,默认值是8个字符
  4. Query OK, 0 rows affected (0.00 sec)
  5. mysql> alter user user() identified by "123456"; //修改登陆密码
  6. Query OK, 0 rows affected (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123456。

退出“mysql> ”环境,重新登录验证,必须采用新的密码才能登入:

  1. mysql> exit                                 //退出 mysql> 环境
  2. Bye
  3. [root@localhost ~]# mysql -u root -p        //重新登录
  4. Enter password:                             //输入新设置的密码
  5. Welcome to the MySQL monitor. Commands end with ; or \g.
  6. Your MySQL connection id is 15
  7. Server version: 5.7.17 MySQL Community Server (GPL)
  8.  
  9. Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  10.  
  11. Oracle is a registered trademark of Oracle Corporation and/or its
  12. affiliates. Other names may be trademarks of their respective
  13. owners.
  14.  
  15. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

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:

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:

  1. [root@dbsvr1 ~]# mysql -uroot -p123456         //紧挨着选项,不要空格
  2. mysql: [Warning] Using a password on the command line interface can be insecure.
  3. Welcome to the MySQL monitor. Commands end with ; or \g.
  4. Your MySQL connection id is 16
  5. Server version: 5.7.17 MySQL Community Server (GPL)
  6.  
  7. Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  8.  
  9. Oracle is a registered trademark of Oracle Corporation and/or its
  10. affiliates. Other names may be trademarks of their respective
  11. owners.
  12.  
  13. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  14.  
  15. mysql> exit                                 //退出已登录的mysql> 环境
  16. 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;

  1. [root@dbsvr1 ~]# mysql -h 127.0.0.1 –u root –p
  2. Enter password:
  3. Welcome to the MySQL monitor. Commands end with ; or \g.
  4. Your MySQL connection id is 17
  5. Server version: 5.7.17 MySQL Community Server (GPL)
  6.  
  7. Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  8.  
  9. Oracle is a registered trademark of Oracle Corporation and/or its
  10. affiliates. Other names may be trademarks of their respective
  11. owners.
  12.  
  13. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  14.  
  15. mysql> exit                                 //退出已登录的mysql环境
  16. Bye

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:

1)查看现有的库

  1. mysql> show databases; //查看现有的库
  2. +--------------------+
  3. | Database |
  4. +--------------------+
  5. | information_schema |                             //信息概要库
  6. | mysql |                             //授权库
  7. | performance_schema |                             //性能结构库
  8. | sys |                             //系统元数据库
  9. +--------------------+
  10. 4 rows in set (0.15 sec)

2)切换/使用指定的库

  1. mysql> use sys; //切换到sys库
  2. Database changed
  3. mysql> select database();                          //确认当前所在的库
  4. +------------+
  5. | DATABASE() |
  6. +------------+
  7. | sys |
  8. +------------+
  9. 1 row in set (0.00 sec)

切换到mysql库:

  1. mysql> use mysql; //切换到mysql库
  2. Reading table information for completion of table and column names
  3. You can turn off this feature to get a quicker startup with -A
  4.  
  5. Database changed
  6. mysql> select database();                         //确认当前所在的库
  7. +------------+
  8. | DATABASE() |
  9. +------------+
  10. | mysql |
  11. +------------+
  12. 1 row in set (0.00 sec)
  13. 5 rows in set (0.00 sec)

3)新建名为newdb的库,确认结果:

  1. mysql> create database newdb; //新建名为newdb的库
  2. Query OK, 1 row affected (0.00 sec)
  3.  
  4. mysql> show databases;
  5. +--------------------+
  6. | Database |
  7. +--------------------+
  8. | information_schema |
  9. | mydb |                         //新建的mydb库
  10. | mysql |
  11. | newdb |                         //新建的newdb库
  12. | performance_schema |
  13. | sys |
  14. +--------------------+
  15. 6 rows in set (0.00 sec)

4)删除指定的库

  1. mysql> drop database newdb; //删除名为newdb的库
  2. Query OK, 0 rows affected (0.01 sec)
  3.  
  4. mysql> show databases;                         //确认删除结果,已无newdb库
  5. +--------------------+
  6. | Database |
  7. +--------------------+
  8. | information_schema |
  9. | mydb |
  10. | mysql |
  11. | performance_schema |
  12. | sys |
  13. +--------------------+
  14. 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:

  1. mysql> use mysql;
  2. Reading table information for completion of table and column names
  3. You can turn off this feature to get a quicker startup with -A
  4.  
  5. Database changed
  6. mysql> show tables;
  7. +---------------------------+
  8. | Tables_in_mysql |
  9. +---------------------------+
  10. | columns_priv |
  11. | db |
  12. | engine_cost |
  13. | event |
  14. | func |
  15. | general_log |
  16. | gtid_executed |
  17. | help_category |
  18. | help_keyword |
  19. | help_relation |
  20. | help_topic |
  21. | innodb_index_stats |
  22. | innodb_table_stats |
  23. | ndb_binlog_index |
  24. | plugin |
  25. | proc |
  26. | procs_priv |
  27. | proxies_priv |
  28. | server_cost |
  29. | servers |
  30. | slave_master_info |
  31. | slave_relay_log_info |
  32. | slave_worker_info |
  33. | slow_log |
  34. | tables_priv |
  35. | time_zone |
  36. | time_zone_leap_second |
  37. | time_zone_name |
  38. | time_zone_transition |
  39. | time_zone_transition_type |
  40. | user | //存放数据库用户的表
  41. +---------------------------+
  42. 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:

  1. mysql> desc columns_priv\G         //查看表结构,以列表形式展现,末尾不用分号
  2. *************************** 1. row ***************************
  3. Field: Host
  4. Type: char(60)
  5. Null: NO
  6. Key: PRI
  7. Default:
  8. Extra:
  9. *************************** 2. row ***************************
  10. Field: Db
  11. Type: char(64)
  12. Null: NO
  13. Key: PRI
  14. Default:
  15. Extra:
  16. *************************** 3. row ***************************
  17. Field: User
  18. Type: char(32)
  19. Null: NO
  20. Key: PRI
  21. Default:
  22. Extra:
  23. *************************** 4. row ***************************
  24. Field: Table_name
  25. Type: char(64)
  26. Null: NO
  27. Key: PRI
  28. Default:
  29. Extra:
  30. *************************** 5. row ***************************
  31. Field: Column_name
  32. Type: char(64)
  33. Null: NO
  34. Key: PRI
  35. Default:
  36. Extra:
  37. *************************** 6. row ***************************
  38. Field: Timestamp
  39. Type: timestamp
  40. Null: NO
  41. Key:
  42. Default: CURRENT_TIMESTAMP
  43. Extra: on update CURRENT_TIMESTAMP
  44. *************************** 7. row ***************************
  45. Field: Column_priv
  46. Type: set('Select','Insert','Update','References')
  47. Null: NO
  48. Key:
  49. Default:
  50. Extra:
  51. 7 rows in set (0.01 sec)

查看columns_priv表的结构,以表格形式展现:

  1. mysql> desc columns_priv;         //查看表结构,以表格形式展现末尾需要有分号
  2. +-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
  3. | Field | Type | Null | Key | Default | Extra |
  4. +-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
  5. | Host | char(60) | NO | PRI | | |
  6. | Db | char(64) | NO | PRI | | |
  7. | User | char(32) | NO | PRI | | |
  8. | Table_name | char(64) | NO | PRI | | |
  9. | Column_name | char(64) | NO | PRI | | |
  10. | Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
  11. | Column_priv | set('Select','Insert','Update','References') | NO | | | |
  12. +-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
  13. 7 rows in set (0.00 sec)

上述操作中,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“desc columns_priv;”,与以下操作的效果是相同的:

  1. mysql> desc mysql.columns_priv;
  2. +-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
  3. | Field | Type | Null | Key | Default | Extra |
  4. +-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
  5. | Host | char(60) | NO | PRI | | |
  6. | Db | char(64) | NO | PRI | | |
  7. | User | char(16) | NO | PRI | | |
  8. | Table_name | char(64) | NO | PRI | | |
  9. | Column_name | char(64) | NO | PRI | | |
  10. | Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
  11. | Column_priv | set('Select','Insert','Update','References') | NO | | | |
  12. +-------------+----------------------------------------------+------+-----+-------------------+-----------------------------+
  13. 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:

  1. mysql> use mydb;
  2. Database changed

新建pwlist表:

  1. mysql> create table pwlist(
  2. -> name char(16) not null,
  3. -> password char(48)default '',
  4. -> primary key(name)
  5. -> );
  6. Query OK, 0 rows affected (0.38 sec)

确认新创建的表:

  1. mysql> show tables;
  2. +----------------+
  3. | Tables_in_mydb |
  4. +----------------+
  5. | pwlist |                                 //新建的pwlist表
  6. +----------------+
  7. 1 rows in set (0.01 sec)

查看pwlist表的字段结构:

  1. mysql> desc pwlist;
  2. +----------+----------+------+-----+---------+-------+
  3. | Field | Type | Null | Key | Default | Extra |
  4. +----------+----------+------+-----+---------+-------+
  5. | name | char(16) | NO | PRI | NULL | |
  6. | password | char(48) | YES | | | |
  7. +----------+----------+------+-----+---------+-------+
  8. 2 rows in set (0.01 sec)

4)删除指定的表

删除当前库中的pwlist表:

  1. mysql> drop table pwlist;
  2. Query OK, 0 rows affected (0.01 sec)

确认删除结果:

  1. mysql> show tables;
  2. 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:

  1. mysql> CREATE TABLE mydb.student(
  2. -> 学号 char(9) NOT NULL,
  3. -> 姓名 varchar(4) NOT NULL,
  4. -> 性别 enum('男','女') NOT NULL,
  5. -> 手机号 char(11) DEFAULT '',
  6. -> 通信地址 varchar(64),
  7. -> PRIMARY KEY(学号)
  8. -> ) DEFAULT CHARSET=utf8;                 //手工指定字符集,采用utf8
  9. Query OK, 0 rows affected (0.31sec)

查看student表的字段结构:

  1. mysql> DESC mydb.student;
  2. +--------------+-------------------+------+-----+---------+-------+
  3. | Field | Type | Null | Key | Default | Extra |
  4. +--------------+-------------------+------+-----+---------+-------+
  5. | 学号 | char(9) | NO | PRI | NULL | |
  6. | 姓名 | varchar(4) | NO | | NULL | |
  7. | 性别 | enum('男','女') | NO | | NULL | |
  8. | 手机号 | char(11) | YES | | | |
  9. | 通信地址 | varchar(64) | YES | | NULL | |
  10. +--------------+-------------------+------+-----+---------+-------+
  11. 5 rows in set (0.00 sec)

查看student表的实际创建指令:

  1. mysql> SHOW CREATE TABLE mydb.student;
  2. +---------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  3. |Table |Create Table |
  4. +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  5. | student | CREATE TABLE `student` (
  6. `学号` char(9) NOT NULL,
  7. `姓名` varchar(4) NOT NULL,
  8. `性别` enum('男','女') NOT NULL,
  9. `手机号` char(11) DEFAULT '',
  10. `通信地址` varchar(64) DEFAULT NULL,
  11. PRIMARY KEY (`学号`)
  12. ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
  13. +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  14. 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。

  1. [root@dbsvr1 ~]# vim /etc/my.cnf                         //修改运行服务配置
  2. [mysqld]
  3. .. ..
  4. character_set_server=utf8
  5.  
  6. [root@dbsvr1 ~]# systemctl restart mysqld                 //重启服务
  7. .. ..
  8. [root@dbsvr1 ~]# mysql –u root -p
  9. Enter password:
  10. .. ..
  11. mysql> SHOW VARIABLES LIKE 'character%';                 //确认更改结果
  12. +--------------------------+----------------------------+
  13. | Variable_name | Value |
  14. +--------------------------+----------------------------+
  15. | character_set_client | utf8 |
  16. | character_set_connection | utf8 |
  17. | character_set_database | utf8 |
  18. | character_set_filesystem | binary |
  19. | character_set_results | utf8 |
  20. | character_set_server | utf8 |
  21. | character_set_system | utf8 |
  22. | character_sets_dir | /usr/share/mysql/charsets/ |
  23. +--------------------------+----------------------------+
  24. 8 rows in set (0.03 sec)

3 MySQL 数据类型

3.1 问题

3.2 步骤

实现此案例需要按照如下步骤进行。

步骤一:创建studb库、stuinfo表

1)新建studb库,并切换到studb库

  1. mysql> CREATE DATABASE studb;
  2. Query OK, 1 row affected (0.00 sec)
  3. mysql> USE studb;
  4. Database changed

2)新建stuinfo表

假定stuinfo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)。

  1. mysql> CREATE TABLE stuinfo (
  2. -> name varchar(16) NOT NULL,
  3. -> gender enum('male','femal') DEFAULT 'male',
  4. -> birth date NOT NULL,
  5. -> job varchar(16) DEFAULT '',
  6. -> relation varchar(24) NOT NULL,
  7. -> PRIMARY KEY(name)
  8. -> );
  9. Query OK, 0 rows affected (0.61sec)

查看stuinfo表的字段结构:

  1. mysql> DESC stuinfo;
  2. +----------+----------------------+------+-----+---------+-------+
  3. | Field | Type | Null | Key | Default | Extra |
  4. +----------+----------------------+------+-----+---------+-------+
  5. | name | varchar(16) | NO | PRI | NULL | |
  6. | gender | enum('male','femal') | YES | | male | |
  7. | birth | date | NO | | NULL | |
  8. | job | varchar(16) | YES | | | |
  9. | relation | varchar(24) | NO | | NULL | |
  10. +----------+----------------------+------+-----+---------+-------+
  11. 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

  1. mysql> SELECT now();
  2. +---------------------+
  3. | now() |
  4. +---------------------+
  5. | 2017-04-02 04:02:42 |
  6. +---------------------+
  7. 1 row in set (0.00 sec)

2)使用sysdate()查看系统日期和时间

  1. mysql> SELECT sysdate();
  2. +---------------------+
  3. | sysdate() |
  4. +---------------------+
  5. | 2017-04-02 04:03:21 |
  6. +---------------------+
  7. 1 row in set (0.00 sec)

3)使用curdate()获得当前的日期,不含时间

  1. mysql> SELECT curdate();
  2. +------------+
  3. | curdate() |
  4. +------------+
  5. | 2017-04-02 |
  6. +------------+
  7. 1 row in set (0.00 sec)

4)使用curtime()获得当前的时间,不含日期

  1. mysql> SELECT curtime();
  2. +-----------+
  3. | curtime() |
  4. +-----------+
  5. | 04:04:55 |
  6. +-----------+
  7. 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

  1. mysql> SELECT year(now()),month(now()),day(now());
  2. +-------------+--------------+------------+
  3. | year(now()) | month(now()) | day(now()) |
  4. +-------------+--------------+------------+
  5. | 2017 | 4 | 2 |
  6. +-------------+--------------+------------+
  7. 1 row in set (0.00 sec)

6)获取系统日期时间中的月份、日

  1. mysql> SELECT month(sysdate()),day(sysdate());
  2. +------------------+----------------+
  3. | month(sysdate()) | day(sysdate()) |
  4. +------------------+----------------+
  5. | 4 | 2 |
  6. +------------------+----------------+
  7. 1 row in set (0.00 sec)

7)获取系统日期时间中的时刻

  1. mysql> SELECT time(sysdate());
  2. +-----------------+
  3. | time(sysdate()) |
  4. +-----------------+
  5. | 04:06:08 |
  6. +-----------------+
  7. 1 row in set (0.00 sec)