在学校的时候,有这么一个现象,有的孩子很用功,成绩却一直不高不低,每一次的 考试就是对他心理承受的一次考验!也有这么几个人,平时不怎么用功,却在最后 一场赛跑中占尽风头!还有很少的人,太用功,太用功!走进了理想的大学!为什 么会这样,为什么不
在学校的时候,有这么一个现象,有的孩子很用功,成绩却一直不高不低,每一次的考试就是对他心理承受的一次考验!也有这么几个人,平时不怎么用功,却在最后
一场赛跑中占尽风头!还有很少的人,太用功,太用功!走进了理想的大学!为什
么会这样,为什么不是下功夫最多的孩子得到的最多!反而会出现一种反
常的现象?先哲的一句名言“天道酬勤”有错了吗?
今天,老师为我们讲解怎么学习数据库,在那字里行间,我渐渐找到了答案!
我们做任何事情,学习任何一门课程,我们要高效,高速,高质的完成!这里
至关重要的一个东西就是,找一个“眼”!有了这个“眼”我们就能通观全局!做到牵一
发而动全身,做到瞬间完成他人十倍乃至百倍的工作!
让我们先建立这么一个信念!我们行!我们可以!这个一定可以!自信,相信
是一切的前提!
下面来说找眼步骤:
1, 迅速了解全局
这是前提,拿读书举例,首先要速读,不要记忆,要通观全局,分析出书的思
路,理清各个部分之间的关系,有时候我们找的关系。不一定是最合适的,但是一
定要能说服自己,一定要让自己合上书也能讲个大概!这时候要有一张大概且简单
的图在纸上,或者大脑里!
2, 多角度观察
理清了各个部分的关系,然后就是找一个或者多个核心,可以形象的理解为刨
树找“根”的过程,就像一个正弦波,从频域和值域完全是两个图,就可以是两个中
心,他们都是“根”,知识表现的方面不同!这时候要有一张图,各个部分关系复杂
,却有条有理!
3, 综合找眼
结合前两步,分析两张图,做总结性思考,让关系简单且密切,结合我们以往
的生活经历,把“眼”放到生活中,让他们所有的元素都围绕着一件事慢慢展开,娓
娓道来!让自己忘不掉整个故事!
这是数据库的例子大家一眼就能看出来,“眼”就是数据
当我们找到“眼”了工作已经进行了大半,接下来就是用我们的作业,工作,
任务来充实整个结构,让它向外衍生!
有了这一系列的办法,我们就能快速、高效、高质地掌握一种知识!这样,
我们就能轻松快乐的完成一项工作!没有加班!让高考的学子不要苦恼,轻松过
独木桥!

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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