Command Meaning Definition

Usually speaking of foreign keys, we only mention "the purpose of the foreign key is to determine the referential integrity of the data." However, what foreign keys specifically include the actions and meanings? 1, set the outer chain: (1), create a foreign key through create table: see 2 lines of code is built in the table command: create table city (... key idx_fk_country_id (country_id), constrain ...

With the proliferation of data volume, Mysql+memcache has not met the needs of large-scale Internet applications, many organizations have chosen Redis as its architectural complement, however, redis the use of the threshold is not low, such as not supporting SQL, here for everyone to share the Redis use of the full raiders. Redis, one of the most closely watched NoSQL databases, has been used by many well-known internet companies, such as Sina Weibo, Pinterest and Viacom. However, being born with no support for SQL makes him look difficult ...

Editor's note: The last period of time reproduced in the "5 minutes to understand docker! "Very popular, a short 1500 words, let everyone quickly understand the Docker." Today, I saw the author make a new novel, and immediately turned over. The reason to call this code reading as a fantasy trip is because the author Liu Mengxin (@oilbeater) in the process of reading Docker source, found a few interesting things: from the code point of view Docker did not start a new development mechanism, but the existing tested isolation security mechanism to use the full use, Including Cgroups,c ...

If a computer manufacturer, its database holds machine and accessories product information. The table used to save the whole product information is called pc; the table used to save the parts supply information is called parts. There is a field in the pc table, used to describe the type of CPU used in this computer; there is a field in the parts table, the description of the CPU model, we can think of it as a list of all CPU models. Obviously, the CPU used by this manufacturer must be a model that exists in the supply information sheet. At this time, two tables ...

Hive in the official document of the query language has a very detailed description, please refer to: http://wiki.apache.org/hadoop/Hive/LanguageManual, most of the content of this article is translated from this page, Some of the things that need to be noted during the use process are added. Create tablecreate [EXTERNAL] TABLE [IF not EXISTS] table_name [col_name data_t ...

Some of the functions in the shell are implemented by special symbols as control characters, as described above. This creates a problem if a filename contains exactly those characters, such as; , it is difficult to operate on it. Use pager to browse this file pager xxx pager will soon return an error message because there is no file name for the action object. The shell then reports that there is no XXX command in the system. This is because the shell will be in the filename; Resolves to execute in order ...

We believe that the goal-oriented design method consists of 4 p, i.e. process, pattern, principles, practices (processes, patterns, principles, practices), and I will discuss the first 3 p. Interaction design is generally a difficult and messy task, and interaction designers are often asked to imagine and define in a tight schedule a possible use of the latest technology, and no one has seen, we must have a deep understanding of the complex areas of products, must balance the competitive priorities, Must understand the constraints of the technology used and the machine ...

Henry and I are working on an examination of the big data and its true meaning. Large data is a popular language. As with many popular words, the word "big data" is a bit overused, but it contains some real usability and technology. 　　We decided to analyze the big data on this topic and try to find out the authenticity of it and what they mean to storage solutions. Henry started this series with a good introduction. His definition of big data is the best definition I have ever seen. So I'm going to repeat this definition: Big data is turning data into information ...

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Absrtact: Feng Dahui (fenng) has shared a story about hackers in his micro-credit public accounts, which is a legendary novel style, which many people have read before expressing their belief. Fenng to this comment: "People questioned may not be ignorant, but things Feng Dahui (fenng) in its micro-letter public account" gossip "on the share of a" hacker "story, the article is quite legendary novel style, many people read after said" Can't believe. " "The people who are questioning may not be ignorant, but things are more than they know," Fenng said.