Mysql Trigger If

In peacetime is asked the most questions about the MySQL database performance optimization issues, so recently intended to write a MySQL database performance optimization of the series of articles, I hope that the junior high level MySQL DBA and other interested in MySQL performance of friends to help. Databases are IO-intensive applications whose primary responsibility is data management and storage. And we know that the time to read a database from memory is the microsecond level, and reading an IO from a common hard disk is at the millisecond level, both ...

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 ...

MySQL database sql statement commonly used optimization methods 1. Query optimization, should try to avoid full table scan, should first consider where and order by the columns involved in the establishment of the index. 2. Should be avoided in the where clause on the field null value judgment, otherwise it will cause the engine to abandon the use of indexes and full table scan, such as: select id from t where num is null You can set the default value of num 0, to ensure that Num column table does not null value ...

Overview 2.1.1 Why a Workflow Dispatching System A complete data analysis system is usually composed of a large number of task units: shell scripts, java programs, mapreduce programs, hive scripts, etc. There is a time-dependent contextual dependency between task units In order to organize such a complex execution plan well, a workflow scheduling system is needed to schedule execution; for example, we might have a requirement that a business system produce 20G raw data a day and we process it every day, Processing steps are as follows: ...

Overview How to deal with high concurrency, large traffic? How to ensure data security and database throughput? How do I make data table changes under massive data? Doubanfs and DOUBANDB characteristics and technology implementation? During the QConBeijing2009, the Infoq Chinese station was fortunate enough to interview Hong Qiangning and discuss related topics. Personal Profile Hong Qiangning, graduated from Tsinghua University in 2002, is currently the chief architect of Beijing Watercress Interactive Technology Co., Ltd. Hong Qiangning and his technical team are committed to using technology to improve people's culture and quality of life ...

The intermediary transaction SEO diagnoses Taobao guest Cloud host technology Hall August 19, 2010, Hdwiki series builds the station lecture 13th period invited Hdwiki Product manager Het for everybody to uncover Hdwiki 5.0 Beta's birth course. Hdwiki as China's first independent intellectual property rights of the Chinese wiki (wiki) system, by Interactive Online (Beijing) Technology Co., Ltd. officially launched on November 28, 2006, and strive to give a large number of wiki (wiki) enthusiasts at home and abroad to provide a free ...

MongoDB company formerly known as 10gen, founded in 2007, in 2013 received a sum of 231 million U.S. dollars in financing, the company's market value has been increased to 1 billion U.S. dollar level, this height is well-known open source company Red Hat (founded in 1993) 20 's struggle results. High-performance, easy to expand has been the foothold of the MongoDB, while the specification of documents and interfaces to make it more popular with users, this point from the analysis of the results of Db-engines's score is not difficult to see-just 1 years, MongoDB finished the 7th ...

http://www.aliyun.com/zixun/aggregation/13461.html"> MongoDB, formerly known as 10gen, was founded in 2007 and after receiving a total of $ 231 million in 2013, the company's market capitalization has risen to 10 Billion dollar level, which is the result of 20 years of Red Hat, a well-known open-source company founded in 1993. High performance and easy scalability have been the foundation of MongoDB and meanwhile standardized documents ...

Foreign key role: Maintain data consistency, integrity, the main purpose is to control the data stored in the foreign key table. So that the two forms related, the foreign key can only refer to the value of the column in the surface! For example: ab two tables a table has the customer number, customer name b table stored in each customer's order After the foreign key You can only delete clients in Table a if you do not have Customer x in the b table. Prerequisites: The columns in this table must be the same as the foreign keys (the foreign key must be a foreign key). Specify ...

The outlet of the specialty of e-commerce where a senior practitioner to the E-commerce Professional school, teachers, students of a letter this letter Hui Jian wrote almost one weeks, modified a lot of times, because Hui Jian saw a few students majoring in E-commerce to become a porter, is really not see the kind of helpless eyes. The parents worked hard to save money, read four years of university, came out but can only go to chores. 　　Why? 　　Here is the reflection of Hui Jian. One, the social demand many and the embarrassment of e-commerce graduates two, society ...