Oracle Sql Sum Case

We want to do not only write SQL, but also to do a good performance of the SQL, the following for the author to learn, extract, and summarized part of the information to share with you! (1) Select the most efficient table name order (valid only in the Rule-based optimizer): The ORACLE parser processes the table names in the FROM clause in Right-to-left order, and the last table in the FROM clause (the underlying table driving tables) is processed first, In the case where multiple tables are included in the FROM clause, you must select the table with the least number of records as the underlying table. If...

Intermediary transaction SEO diagnosis Taobao guest Cloud host Technology Hall log is a very broad concept in computer systems, and any program may output logs: Operating system kernel, various application servers, and so on. 　　The content, size and use of the log are different, it is difficult to generalize. The logs in the log processing method discussed in this article refer only to Web logs. There is no precise definition, which may include, but is not limited to, user access logs generated by various front-end Web servers--apache, LIGHTTPD, Tomcat, and ...

A news incident last week attracted media attention, with nearly 450,000 passwords from 450,000 yahoo services called ' Yahoo Voice ' hacked. The comment on the incident said that hackers mainly through SQL injection (SQL injection) technology is the hacker from the database to obtain information and then release the information of the main technology adopted. Even if the original article is modified, you can find the error if you do a check. Technology is the same, as every more in-depth discussion can find new problems. ...

Since Amason launched SimpleDB, distributed data storage systems based on Key-value key values have received widespread attention, similar systems include Apache COUCHDB, and the recent blockbuster Google App Engine based on the BigTable Datastore API, there is no doubt that the distributed data storage system provides better lateral scalability, is the future direction of development. But at this stage, compared with the traditional RDBMS, there are some gaps and deficiencies. Ryan P ...

The information about the big data is overwhelming and dazzling. Although the information is wonderful, we also see the value behind the big data, but many companies do not know how to do it. In a pragmatic manner, using low cost, high speed capture and real-time analysis of large data to obtain the key information needed for core business and strategic decision, so as to enhance the level of business management and strategic decision, and ultimately create huge commercial value, perhaps the best interpretation of large data value. In the process of analyzing large data, the traditional bi (business intelligence) approach is that IT staff ...

As the most popular open source database, MySQL is widely used in Web applications and other small and medium-sized projects. However, in many large IT companies, MySQL has gradually deviated from the original open source version after being highly optimized and customized, more like a branch, such as the Webscalesql of Facebook, which was not long ago open source. 　　Recently, Mr. Xiong has published a blog post, from the perspective of large-scale web site architecture development of the changes in MySQL application, here for you to share. This article mainly describes the different and ...

I was once a staunch supporter of Hadoop. I like it to handle PB-level data easily, like it can extend operations to thousands of-node http://www.aliyun.com/zixun/aggregation/13452.html "> Distributed computing Capabilities, It also likes the flexibility of storing and loading data. But after a series of explorations and use, I was very disappointed with Hadoop. Here's why I don't use Hadoop for data analysis ...