Unsigned Data Type

Either in the pitiful free database space or large e-commerce sites, reasonable design table structure, make full use of space is very necessary. This requires that we have a full understanding of the commonly used MySQL data types for database systems. Now I will write down my little experience to share with you. The numeric type of the MySQL data type The numeric type is divided into three categories according to my classification: integer classes, decimal classes, and numeric classes. My so-called "digital class" refers to DECIMAL and NUMERIC, which are the same type. It is strictly speaking not ...

I. Introduction We often see some similar in the program disassembled code 0 × 32118965 this address, the operating system called linear address, or virtual address. What is the use of virtual address? Virtual address is how to translate into physical memory address? This chapter will give a brief account of this. 1.1 Linux Memory Addressing Overview Modern operating systems are in 32-bit protected mode. Each process can generally address 4G of physical space. But our physical memory is generally hundreds of M, the process can get 4 ...

One, the mail system installs 1, the package installs Postfix+courier-imap+cyrus-sasl+pam_mysql+mysql this kind of installation method is simple and easy, installs under the Debian more convenient: # apt Install Courier-pop postfix-mysql postfix-tls courier-authdaemon\courier-authmysql libpam-mysql l ...

DEDECMS database Structure table name: Dede_feedback field description is as follows: Table name: Dede_feedback (ENGINE=MYISAM/CHARSET=GBK) Description: Comment 6184.html "> Data table field name description Specific parameter userhttp://www.aliyun.com/zixun/aggregation/11696.html ">name username ...

1. Boxing, unpacking or aliases many of the introduction of C #. NET learning experience books on the introduction of the int-> Int32 is a boxing process, the reverse is the process of unpacking. This is true of many other variable types, such as short <-> int16,long <->int64. For the average programmer, it is not necessary to understand this process, because these boxes and unboxing actions can be automatically completed, do not need to write code to intervene. But we need to remember that ...

Absrtact: Mobile phones have become a necessity for most people. At present, China's mobile phone users have exceeded 1.1 billion, on average, every 10 people have 8 mobile phones. At the same time, spam message also flooded, all kinds of advertising, fraud information seriously affect our lives. These junk short phones have become a necessity for most people. At present, China's mobile phone users have exceeded 1.1 billion, on average, every 10 people have 8 mobile phones. At the same time, spam message also flooded, all kinds of advertising, fraud information seriously affect our lives. Where does this junk text message come from? Who is to be supervised? Today is "World telecom ...

Traditional client and server-side software technologies use a software solution called sockets to establish a connection. The use of sockets has not changed as the industry has grown from a static, fat client to a mobile thin client. But over the years, sockets have changed their shape and become more complex. As a result, this technology becomes difficult to understand, not to mention a comprehensive understanding of how sockets are used in the enterprise, or how they are used in conjunction with mobile and cloud technologies. This article will help you understand the concept of sockets, the type of sockets you can use for your applications, and use in mobile and cloud solutions ...

DEDECMS database Structure table name: Dede_erradd field description is as follows: Table name: Dede_erradd (ENGINE=MYISAM/CHARSET=GBK) Description: Wrong 6184.html "> Data table field name description describes specific parameters Errtxt error message Mediumtext, title title char not NULL DEFAULT ', aid document ID me ...

First, the importance of the index The index is used to quickly find a column in a particular value of the line. Instead of using an index, MySQL must start with the first record and then read the entire table until it finds the relevant row. The larger the table, the more time it takes. If the table in the query column index, MySQL can quickly reach a location to search the middle of the data file, there is no need to see all the data. Note that if you need to access most of the rows, sequential reads are much faster since we avoid disk searches. If you use Xinhua Dictionary to find "Zhang" the Chinese characters, do not use the directory, then ...

The disadvantage of using HDFS to save a large number of small files with use using the: 1.Hadoop Namenode saves "meta information" data for all files in memory. According to statistics, each file needs to consume NameNode600 bytes of memory. If you need to save a large number of small files will cause great pressure on the namenode. 2. If the use of Hadoop MapReduce small file processing, then the number of Mapper will be the number of small files into a linear correlation (Note: Filei ...