简介 在 Microsoft Access 2002 中,Web 开发 过程已被大大简化。在 Access 中 开发 基于 Web 的应用程序时,我们将创建称为数据访问页的 Web 页。 数据访问页是内容丰富的、基于 HTML 的文档,其中含有可绑定到 Microsoft SQL Server、Microsoft Jet 和 Mic
简介
在 Microsoft Access 2002 中,Web 开发过程已被大大简化。在 Access 中开发基于 Web 的应用程序时,我们将创建称为数据访问页的 Web 页。
数据访问页是内容丰富的、基于 HTML 的文档,其中含有可绑定到 Microsoft SQL Server™、Microsoft Jet 和 Microsoft Project 数据的 Microsoft® ActiveX® 控件。ActiveX 控件管理数据的链接、排序和分组,并使用 ActiveX 数据对象 (ADO) 来获取记录集。
要浏览数据访问页,需要使用 Microsoft Internet Explorer 5.0 或更高版本,以及 Microsoft Office Web Components。与 Microsoft Access 2000 不同,在 Microsoft Access 2002 中,您可以创建并部署包含数据访问页的应用程序,而您的用户无需拥有 Microsoft Office XP 许可证便可以查看这些应用程序。
数据访问页具有一个以数据为中心的、世界级的 HTML 设计环境。它允许用户与其在 Web 上的数据进行交互。如同通常对 Access 所希望的一样,用户也能够执行筛选、排序、保存、撤消、删除以及其他动作。
数据访问页通常最适合于 Intranet 或工作组应用程序,从中人们可以彼此直接合作,这一点与拥有成千上万 Web 站点访问客户的 Internet 应用程序不同。
数据访问页的工作原理
如果查看数据访问页的源代码,将会看到

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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