ps:虽然我没说明版权,但是转载也要说明下啊,至少给我点面子行不? www.2cto.com编外:我们希望作者给个总的题目。。。免得读者看起来不系统 作者:幻泉 2.2.3 数据库 类型的 判断 与各种 数据库 特征 在注入入侵前需要先 判断 数据库 类型,因为各种 数据
ps:虽然我没说明版权,但是转载也要说明下啊,至少给我点面子行不?
www.2cto.com编外:我们希望作者给个总的题目。。。免得读者看起来不系统
作者:幻泉
2.2.3 数据库类型的判断与各种数据库特征
在注入入侵前需要先判断数据库类型,因为各种数据库的SQL注入都各有不同,所以判断数据库类型有利于我们针对特定数据库进行入侵检测。
2.2.3.1 对Access数据库的判断与其特征
通过错误页面判断:
这是上面讲过的图片,其中Microsoft JET Database Engine 错误 80040e14说明他是用JET数据库引擎连接的数据库,而JET是Microsoft Access和Visual Basic使用的一种数据库引擎,所以可以肯定这个页面连接的数据库是微软的Access数据库。
通过查询判断:
加入容错处理的程序不会显示错误信息。所以无法从网页中判断是什么数据库。但是Access存在几个默认系统表我们可以通过查询其默认数据表,来与其他数据库区分。(因为Access数据库的系统表大部分都是唯一的)
正常情况下access是不允许查看系统表的,所以我们需要进行设置来让数据库显示系统表。打开数据库点击工具栏中的工具-选项,勾选“系统对象”选项点确定就会看到系统表了。
Access总共有6个系统表,如下表格:
系统表名 |
系统列名 |
MSysAccessObjects |
ID |
Data |
|
MSysAccessXML |
Id |
LValue |
|
ObjectGuid |
|
ObjectName |
|
|

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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