MySQL操作之DCL

目录

• SQL语句的分类
  • DCL语句

SQL语句的分类

1. DDL（Data Definition Languages）语句：数据定义语言。这些语句定义了不同的数据段、
   
   数据库、表、列、索引等数据库对象的定义。常用的语句关键字主要包括create、drop、alter
   
   等。
2. DML（Data Manipulation Language）语句：数据操纵语句，用于添加、删除、更新和查
   
   询数据库记录，并检查数据完整性，常用的语句关键字主要包括insert、delete、udpate 和
   
   select 等。
3. DCL（Data Control Language）语句：数据控制语句，用于控制不同数据段直接的许可和
   
   访问级别的语句。这些语句定义了数据库、表、字段、用户的访问权限和安全级别。主要的
   
   语句关键字包括grant、revoke 等。

DCL语句

DCL 语句主要是DBA 用来管理系统中的对象权限时所使用，一般的开发人员很少使用。下面

通过一个例子来简单说明一下。

创建一个数据库用户plf，具有对plf数据库中所有表的SELECT/INSERT 权限：

mysql> grant select,insert on plf.* to 'plf'@'%' identified by '123456';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye

[root@mysql ~]# mysql -uplf -p123456 -h 192.168.3.100
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 7
Server version: 5.6.37 Source distribution

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;
ERROR 1044 (42000): Access denied for user 'plf'@'%' to database 'mysql'
mysql> use plf
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

由于权限变更，需要将 plf 的权限变更，收回 INSERT，只能对数据进行 SELECT 操作,这时我们需要使用root账户进行上述操作：

mysql> revoke insert on plf.* from 'plf'@'%';
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye

[root@mysql ~]# mysql -uplf -p123456 -h 192.168.3.100
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: 5.6.37 Source distribution

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 plf
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_plf |
+---------------+
| dept          |
| emp           |
| hk_info       |
| log_info      |
| user_info     |
+---------------+
5 rows in set (0.00 sec)

mysql> insert into dept values(7,'plf');
ERROR 1142 (42000): INSERT command denied to user 'plf'@'192.168.3.100' for table 'dept'
mysql> select*from dept;
+--------+----------+
| deptno | deptname |
+--------+----------+
|      1 | tech     |
|      2 | sale     |
|      3 | hr       |
|      5 | fin      |
+--------+----------+
4 rows in set (0.00 sec)

以上例子中的grant和revoke分别授出和收回了用户plf的部分权限，达到了我们的目的，关于权限的更多内容，将会在第4篇中详细介绍。