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-2147483648 2147483647 0 4294967295 BIGINT 8 -9223372036854775808 9223372036854775807 0 18446744073709551615 　　What is the maximum length of varchar in MySQL? 　　One. VarChar Storage rules: 4.0 versions, varchar (20), refers to a byte , if stored UTF8 kanji, can only save 6 (

should the software be layered? In order to achieve "high cohesion, low coupling." The problem is divided into various solutions, easy to control, easy to extend, easy to allocate resources ... In short, the benefits are many:). 3. The following are mainly JAVA,J2EE models and frameworks: What are the common design patterns? First of all,

what circumstances are indexes, but not used?Indexes do not always take effect, such as the following, which will invalidate the index : If there is or in the condition, even if some of the conditions in the index are not used ( which is why the use of or is minimized ), in the example user_id no index

What this article brings to you is about what is BFC? What is the use of BFC in CSS? , there is a certain reference value, the need for friends can refer to, I hope you have some help.

to help you. 1. For PHP programmers, the main requirement is to write the controller layer in MVC. This is the main job. 2. If a new table is built, write the model layer (data interaction) layer 3. General company static page (HTML+CSS) by the front-end personnel responsible, if not, that

prevent inconsistent data. Database at design time, the primary key plays a very important role.The primary key guarantees that the record is unique and the primary key domain is not empty, and the database management system automatically generates a unique index for the primary key, so the primary key is also a special index.2. There can be multiple unique inde

What is a data warehouse, and what is the difference between a databaseDataWarehouseis a subject-oriented (Subject oriented), integrated (integrate), A relatively stable (non-volatile), data collection that reflects historical changes (timeVariant) to support management decisions. (1) topic-oriented: Index data in the

port can be divided into 3 main categories:1) Accepted ports (well known Ports): from 0 to 1023, they are tightly bound to some services. Usually the communication of these ports clearly indicates the protocol of some kind of service. For example: Port 80 is actually always HTTP traffic.2 registration port (registered Ports): from 1024 to 49151. They are loosely bound to some services. This means that ther

concurrent execution.It's logically not independent,It by the thingThe separation of services.（3）Isolation ofIsolation means that the execution of a transaction cannot be disturbed by other transactions.That is, the operation within a transaction and the data usedOther transactions that are concurrent are isolated,Each transaction that executes concurrently cannot interfere with each other.It requires that

web, you need to develop a php type, and then you must at least understand the http protocol. If tianyao is not good, you 'd better develop a network protocol, see the application layer such as http and ftp from the hardware cable. only when you understand the network can you understand how the web works. For example, the php background language is used for http protocol (of course, apache

1, Kafka is what. Kafka, a distributed publish/subscribe-based messaging system developed by LinkedIn, is written in Scala and is widely used for horizontal scaling and high throughput rates. 2. Create a background Kafka is a messaging system that serves as the basis for th

Answer:1) recursion as an algorithm is widely used in programming language. Refers to the re-entry of functions/procedures/subroutines that invoke themselves directly or indirectly during operation.2) Recursive algorithms are generally used to solve three types of problems:A. The definition of the data is defined by recursion. (Fibonacci (Fibonacci) function)B. The problem solution

The coding aspect has always been not very high, so it is not known about Unicode and UTF-8. Recently accidentally turned to a UTF-8 article, feel the explanation of the very complex, so just thought to write a simple and understandable. Let's begin by explaining some of the coding schemes that are now commonly used:1, in China, the most commonly used in the mainland is GBK18030 code, in addition to the g

; direction 3: Big Data O M and cloud computing. If you are proficient in any direction, there will be no space in the "front (money)" way. What is the big data talent gap? Is Data Big Data engineers well employed? The answer is: Big Data development

redundancy and is not conducive to maintenance.3. How to linkLinking refers to the use of HTML header tags to introduce external CSS files.Example:head> link rel="stylesheet" type="text/css" href="style.css">head>This is the most common and recommended way to introduce CSS. In this way, all CSS code exists only in a separate CSS file, so it has good maintain

2012-07-14 WCDJ The concept of digital signature is easy to understand, and the details are discussed in detail in the commentary. English Original: http://www.youdzone.com/signature.html (by David Youd) Chinese version: http://www.ruanyifeng.com/blog/2011/08/what_is_a_digital_signature.html (by Nanyi) ------------------------------------------------------------------------------------------------------- What