今天在OOW的ACOUG专场分享了Think Different的主题。 今天一天在会场非常的充实。到了会场后先去听了今天的KeyNotes,其中Steve Miranda的云计算的主题以及Andy Mendelsohn的12c数据库对云计算的支持,都是本次大会的重点话题。Oracle 12c中的C指的就是CLOUD
今天在OOW的ACOUG专场分享了Think Different的主题。
今天一天在会场非常的充实。到了会场后先去听了今天的KeyNotes,其中Steve Miranda的云计算的主题以及Andy Mendelsohn的12c数据库对云计算的支持,都是本次大会的重点话题。Oracle 12c中的C指的就是CLOUD,而12c最大的亮点PLUGABLE DB就是Oracle在DB层对云架构的支持。
如果说去年OOW大会只是给出了12c PLUGABLE DATABASE的概念,那么今年OOW上Oracle已经想好要如何用PDB来支持云服务了,甚至我怀疑Oracle来云服务的收费细则都已经定义好了,青铜、白银和黄金三档,每档对应的架构和服务都已经定义清楚,而在各个档之间进行升级也同样进行说明。看来Oracle已经准备利用12c来打造数据库服务云了。只不过以Oracle以往收费的标准,不知道一些不想自己搭建环境、维护数据库的中小企业,能否接受正版云服务的价格。
中午OOW的午饭一如既往的不给力,这种面包、三明治的配置更适合老外,估计大部分国内参会者,这三天午饭会比较郁闷。
下午全程参加了展览大厅的ACOUG活动,首先是Eygle两个优化的主题,然后是Kamus三个关于升级的主题,最后是我的两个主题,一个是ODA,另一个是Think Different。可惜的是,每个主题的时间只有二十分钟,而我们任何一个主题正常时间都应该超过1小时。因此,最终Eygle只讲了一个主题就超过了两个主题的时间,而Kamus最后紧赶慢赶终于完成了三个主题,但是时间方面超了不少。根据他们两个的前车之鉴,我直接选择了现场绝大部分人都想听的Think Different,而舍弃了ODA的主题。其实舍弃ODA也比较可惜,在OOW的现场展示了ODA的最新版本,而我在中午的时候还把最新版的ODA的内容添加到了PPT里面。
剩下一些零碎的时间基本上都在公司的展台帮忙,除了解答问题,当背景合影外,还碰到了不少新、老朋友。
原文地址:20130723 上海OOW第二日, 感谢原作者分享。

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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