一: sql注入原理
原理就是利用服务器执行sql参数时的特殊性,将正常的数据库字段注入特征字符组成新的SQL语句,导致原来的sql语句“变了味”
举一个简单的例子
$id = $_GET['id']; /// id= 10001 OR 1 = 1 #
$qq = $_GET['qq']; // qq= "261414' OR 1 = 1 #"
$sql = "SELECT * FROM `user` WHERE id=$id AND $qq = '".$qq."'";
$results = $db->query($sql);
二: 如何防范:
1. web参数过滤,只允许约定的字符出现,但过于暴力
2. 拼装的sql语句用mysql_real_escape_string方法进行过滤
$username = mysql_real_escape_string($_GET['username']);
3. mysql用户权限设置,不要用root
4. 使用sql注入扫描工具测试
附:
PDO的prepare是怎么防范SQL注入的
当调用prepare()时,查询语句先被发送给了MYSQL,此时只有占位符发送过去,没有用户提交的数据(MYSQL做预编译,一定程度上会优化查询效率,特别是对同个SQL模版进行多次调用时);当调用execute()时,用户提交的值才会传送给MYSQL。从而达到防范SQL注入的目的。.

MySQLoffersvariousstorageengines,eachsuitedfordifferentusecases:1)InnoDBisidealforapplicationsneedingACIDcomplianceandhighconcurrency,supportingtransactionsandforeignkeys.2)MyISAMisbestforread-heavyworkloads,lackingtransactionsupport.3)Memoryengineis

Common security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.

Identifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.

To monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.

The main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.


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