1 資料庫管理系統

我們的生活中無時無刻都在接觸到資料，而資料庫便是通過指定的組織結構將這資料儲存的倉庫，並且隨著網際網路和資訊科技的發展，資料庫也已經從最初只能儲存簡單表格發展到了儲存海量資料的大型分散式模式。

18.2 初始化mariaDB服務程式

MariaDB相對於MYSQL來講確實在功能上有很多擴充套件特性，比如微秒的支援、執行緒池、子查詢優化、組提交、進度報告等。

安裝mariaDB服務程式：

[[email protected] ~]# yum install mariadb mariadb-server
Loaded plugins: langpacks, product-id, subscription-manager
………………省略部分安裝過程………………
Installing:
 mariadb                         x86_64         1:5.5.35-3.el7          rhel7       8.9 M
 mariadb-server                  x86_64         1:5.5.35-3.el7          rhel7        11 M
Installing for dependencie
 perl-Compress-Raw-Bzip2         x86_64         2.061-3.el7             rhel7        32 k
 perl-Compress-Raw-Zlib          x86_64         1:2.061-4.el7           rhel7        57 k
 perl-DBD-MySQL                  x86_64         4.023-5.el7             rhel7       140 k
 perl-DBI                        x86_64         1.627-4.el7             rhel7       802 k
 perl-Data-Dumper                x86_64         2.145-3.el7             rhel7        47 k
 perl-IO-Compress                noarch         2.061-2.el7             rhel7       260 k
 perl-Net-Daemon                 noarch         0.48-5.el7              rhel7        51 k
 perl-PlRPC                      noarch         0.2020-14.el7           rhel7        36 k
………………省略部分安裝過程………………
Complete!
 

啟動mariadb服務程式並新增到開機啟動項中：

為了保證資料庫的安全性，一定要進行初始化工作：

第1步：設定root使用者密碼。
第2步：刪除匿名帳號。
第3步：禁止root使用者從遠端登陸。
第4步：刪除test資料庫並取消對其的訪問許可權。
第5步：重新整理授權表，讓初始化後的設定立即生效。

初始化資料庫服務程式：

[[email protected] ~]# mysql_secure_installation 
/usr/bin/mysql_secure_installation: line 379: find_mysql_client: command not found
NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!
In order to log into MariaDB to secure it, we'll need the current
password for the root user.  If you've just installed MariaDB, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.
Enter current password for root (enter for none): 當前資料庫密碼為空，直接敲擊回車。
OK, successfully used password, moving on...
Setting the root password ensures that nobody can log into the MariaDB
root user without the proper authorisation.
Set root password? [Y/n] y
New password: 輸入要為root使用者設定的資料庫密碼。
Re-enter new password: 重複再輸入一次密碼。
Password updated successfully!
Reloading privilege tables..
 ... Success!
By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.
Remove anonymous users? [Y/n] y（刪除匿名帳號）
 ... Success!
Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.
Disallow root login remotely? [Y/n] y(禁止root使用者從遠端登陸)
 ... Success!
By default, MariaDB comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.
Remove test database and access to it? [Y/n] y(刪除test資料庫並取消對其的訪問許可權)
 - Dropping test database...
 ... Success!
 - Removing privileges on test database...
 ... Success!
Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.
Reload privilege tables now? [Y/n] y(重新整理授權表，讓初始化後的設定立即生效)
 ... Success!
Cleaning up...
All done!  If you've completed all of the above steps, your MariaDB
installation should now be secure.
Thanks for using MariaDB!

設定防火牆對資料庫服務的允許策略：

[[email protected] ~]# firewall-cmd --permanent --add-service=mysql
success
[[email protected] ~]# firewall-cmd --reload
success

使用root使用者登陸到資料庫中：

[[email protected] ~]# mysql -u root -p
Enter password: 此處輸入root使用者在資料庫中的密碼。
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 5
Server version: 5.5.35-MariaDB MariaDB Server
Copyright (c) 2000, 2013, Oracle, Monty Program Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]>

檢視當前已有的資料庫：

MariaDB [(none)]> show databases;
+--------------------+
" Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.01 sec)

修改當前使用者在資料庫中的密碼（示例中的密碼為redhat）：

MariaDB [(none)]> set password = password('redhat');
Query OK, 0 rows affected (0.00 sec)
MariaDB [(none)]> exit
Bye

使用舊的密碼將不能再登陸到資料庫：

[[email protected] ~]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

18.3 管理資料庫與表單資料

關係型資料庫（DataBase）是由一個或多個數據表單(Table)組成的，資料表單則一般會儲存著多個數據記錄（Record）。

18.3.1 建立使用者並授權

建立一個新的資料庫使用者：

建立資料庫使用者的命令:CREATE USER 使用者名稱@主機名 IDENTIFIED BY ‘密碼’;

MariaDB [(none)]> create user [email protected] IDENTIFIED BY 'linuxprobe';
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> 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

檢視新建立的使用者、主機、姓名與密碼資訊：

MariaDB [mysql]> select host,user,password from user where user="luke";
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | luke | *55D9962586BE75F4B7D421E6655973DB07D6869F |
+-----------+------+-------------------------------------------+
1 row in set (0.00 sec)

退出資料庫後使用新使用者登陸：

MariaDB [mysql]> exit
Bye
[[email protected] ~]# mysql -u luke -p
Enter password: 此處輸入luke使用者的資料庫密碼
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 6
Server version: 5.5.35-MariaDB MariaDB Server
Copyright (c) 2000, 2013, Oracle, Monty Program Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

此時只能檢視到一個數據庫：

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.03 sec)

資料庫GRANT命令的授權操作常用方案：

切換回root使用者登陸資料庫並進入到mysql資料庫中：

[[email protected] ~]# mysql -u root -p
MariaDB [(none)]> 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

給予luke使用者對user表單的查詢、更新、刪除、插入許可權：

MariaDB [mysql]> GRANT SELECT,UPDATE,DELETE,INSERT on mysql.user to [email protected];
Query OK, 0 rows affected (0.00 sec)

檢視luke使用者當前的授權：

再次切換到luke使用者後檢視可用的資料庫：

[[email protected] ~]# mysql -u luke -p
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
+--------------------+
2 rows in set (0.01 sec)

進入到mysql資料庫中看到user表單了：

MariaDB [(none)]> 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
MariaDB [mysql]> show tables;
+-----------------+
| Tables_in_mysql |
+-----------------+
| user            |
+-----------------+
1 row in set (0.01 sec)

切換回root使用者後取消剛剛全部的授權：

MariaDB [(none)]> revoke SELECT,UPDATE,DELETE,INSERT on mysql.user from [email protected];
Query OK, 0 rows affected (0.00 sec)

再次檢視luke使用者的授權：

18.3.2 建立資料庫與表單

常用的資料庫表單管理命令有：

建立一個新的資料庫：

MariaDB [(none)]> create database linuxprobe;
Query OK, 1 row affected (0.00 sec)

檢視當前已有的資料庫：

MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| linuxprobe |
| mysql |
| performance_schema |
+--------------------+
4 rows in set (0.04 sec)

切換到指定的資料庫：

MariaDB [(none)]> use linuxprobe;
Database changed

建立新的資料庫表單：

MariaDB [linuxprobe]> create table mybook (name char(15),price int,pages int);
Query OK, 0 rows affected (0.16 sec)

查看錶單的結構描述：

MariaDB [linuxprobe]> describe mybook;
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| name  | char(15) | YES  |     | NULL    |       |
| price | int(11)  | YES  |     | NULL    |       |
| pages | int(11)  | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+
3 rows in set (0.02 sec)

18.3.3 管理表單資料

向表單內插入新的書籍資料：

MariaDB [linuxprobe]> INSERT INTO mybook(name,price,pages) VALUES('linuxprobe','60',518);
Query OK, 1 row affected (0.00 sec)

查看錶單中的資料值：

MariaDB [linuxprobe]> select * from mybook;
+------------+-------+-------+
| name       | price | pages |
+------------+-------+-------+
| linuxprobe |    60 |   518 |
+------------+-------+-------+
1 rows in set (0.01 sec)

將價格修改為55元：

MariaDB [linuxprobe]> update mybook set price=55 ;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

只看書籍的名字和價格：

MariaDB [linuxprobe]> select name,price  from mybook;
+------------+-------+
| name       | price |
+------------+-------+
| linuxprobe |    55 |
+------------+-------+
1 row in set (0.00 sec)

刪除書籍表單中的內容：

MariaDB [linuxprobe]> delete from mybook;
Query OK, 1 row affected (0.01 sec)
MariaDB [linuxprobe]> select * from mybook;
Empty set (0.00 sec)

連續加入4條書籍記錄值：

MariaDB [linuxprobe]> INSERT INTO mybook(name,price,pages) VALUES('linuxprobe1','30',518);
Query OK, 1 row affected (0.05 sec)
MariaDB [linuxprobe]> INSERT INTO mybook(name,price,pages) VALUES('linuxprobe2','50',518);
Query OK, 1 row affected (0.05 sec)
MariaDB [linuxprobe]> INSERT INTO mybook(name,price,pages) VALUES('linuxprobe3','80',518);
Query OK, 1 row affected (0.01 sec)
MariaDB [linuxprobe]> INSERT INTO mybook(name,price,pages) VALUES('linuxprobe4','100',518);
Query OK, 1 row affected (0.00 sec)

where命令用於在資料庫匹配查詢的條件，可用的條件有：

檢視價格大於75元的書籍：

MariaDB [linuxprobe]> select * from mybook where price>75;
+-------------+-------+-------+
| name        | price | pages |
+-------------+-------+-------+
| linuxprobe3 |    80 |   518 |
| linuxprobe4 |   100 |   518 |
+-------------+-------+-------+
2 rows in set (0.06 sec)

搜尋價格不等於80元的書籍：

MariaDB [linuxprobe]> select * from mybook where price!=80;
+-------------+-------+-------+
| name | price | pages |
+-------------+-------+-------+
| linuxprobe1 | 30 | 518 |
| linuxprobe2 | 50 | 518 |
| linuxprobe4 | 100 | 518 |
+-------------+-------+-------+
3 rows in set (0.01 sec)

18.3.4 資料庫的備份與恢復
mysqldump命令用於備份資料庫資料，格式為：“mysqldump [引數] [資料庫名稱]”。

將書籍資料庫檔案（即linuxprobe）匯出到家目錄：

[[email protected] ~]# mysqldump -u root -p linuxprobe > /root/linuxprobeDB.dump
Enter password: 

刪除書籍資料庫：

MariaDB [linuxprobe]> drop database linuxprobe;
Query OK, 1 row affected (0.04 sec)
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.02 sec)

建立一個空的資料庫：

MariaDB [(none)]> create database linuxprobe;
Query OK, 1 row affected (0.00 sec)

匯入剛剛備份的資料庫：

[[email protected] ~]# mysql -u root -p linuxprobe < /root/linuxprobeDB.dump 
Enter password: 

果然又看到了剛剛建立的mybook表單：

[[email protected] ~]# mysql -u root -p
MariaDB [(none)]> use linuxprobe;
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
MariaDB [linuxprobe]> show tables;
+----------------------+
| Tables_in_linuxprobe |
+----------------------+
| mybook               |
+----------------------+
1 row in set (0.05 sec)