本文示例源代码或素材下载 事情是这样的,我的女朋友想要对日常生活的开销做个记录,以便控制花钱的尺度。看她每日用笔头记录,然后和我抢电脑用,曰:要用附件中的计算器统计结果,每每如此 ,不胜其烦,就给她做了一个个人家庭记帐系统,一劳永逸解决问题
本文示例源代码或素材下载
事情是这样的,我的女朋友想要对日常生活的开销做个记录,以便控制花钱的尺度。看她每日用笔头记录,然后和我抢电脑用,曰:要用附件中的计算器统计结果,每每如此 ,不胜其烦,就给她做了一个个人家庭记帐系统,一劳永逸解决问题。期间用到了ADO操作Access数据库,在网上找了若干关于ADO的资料结合实践总结了一点使用心得如下 ,供有相同需求的朋友参考:
附带了那个个人记帐系统,运行的界面如下:

VC++下使用ADO编写数据库程序
准备:
(1)、引入ADO类 #import "c:\program files\common files\system\ado\msado15.dll" \<br>no_namespace \<br>rename ("EOF", "adoEOF")
(2)、初始化COM
在MFC中可以用AfxOleInit();非MFC环境中用: CoInitialize(NULL);<br>CoUnInitialize();
(3)#import 包含后就可以用3个智能指针了:_ConnectionPtr、_RecordsetPtr和_CommandPtr
1.连接和关闭数据库 (1)连接
例子:连接Access数据库
m_pConnection.CreateInstance(__uuidof(Connection));<br>try <br>{ <br> // 打开本地Access库Demo.mdb<br> m_pConnection->Open("Provider=Microsoft.Jet.OLEDB.4.0;DataSource=Demo.mdb",<br> "","",adModeUnknown);<br>}<br>catch(_com_error e)<br>{<br> AfxMessageBox("<strong>数据库</strong>连接失败,确认<strong>数据库</strong>Demo.mdb是否在当前路径下!");<br> return FALSE;<br>}
(2)、关闭
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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

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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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