sql-primary key, foreign key, index

Label:The role of the primary and foreign keys of sql:Foreign key value rule: A null value or a reference primary key value.(1) When a non-null value is inserted, it cannot be inserted if the value is not in the primary key table.(2) When updating,

Talking about the security of cloud database

Tags: database security Google Internet e-mail cloud PlatformA cloud database is a database that is optimized or deployed to a virtual computing environment. The benefits of pay-as-you-demand, on-demand scaling, high availability, and storage

Analysis of binary Conversion decimal algorithm

Label:In Java there is a way to swap out a ready-made system: Public classconversion of decimal to each binary { Public Static voidMain (string[] args) {//The mechanism that Java has implemented: decimal conversion into binary intdecimal = 10;

The difference between a process and a thread

Label:The thread's dividing scale is smaller than the process, which makes the multi-thread procedure high concurrency.In addition, the process has a separate memory unit during execution, and multiple threads share memory, which greatly improves

Official example of Crystal Report

Label:Original: Official example of Crystal ReportList of. NET application instances developed using C # and C++.net----------------------------------OverviewThis document lists all of the. NET application instances that are available on the Crystal


Label:Principle and application of com,dcom1. DCOMThe process transparency of COM is manifested in the Component object and the client program can have their own process space, also can share the same process space, COM is responsible for the

Economy 64 ... 77

Label:From April 2014 securities B to 1 yuan price began to go on sale to December 17, 2014, the value of the restoration of the highest price rose to 6.5 yuan, rose 500%+! But then there was a terrible drop, down to just 3.9, down to 40% by

Writes 4 methods of the same name, implements two integers, two real numbers, a real number, an integer, and an integer sum of a real number. Call these 4 methods in the keynote function to calculate the related values. (Overloading of methods)

Label:1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSystem.Threading.Tasks;6 7 namespaceConsoleApplication78 {9 class ProgramTen { One Static voidMain (string[] args) A { -

DSN establishes a Dream 7 (DM) connection

Label:(DSN) Data Source NameThe ODBC Data Source Administrator provides three types of DSNs, User DSN, System DSN, and File DSN, respectively.whichThe user DSN saves the appropriate configuration information in the Windows registry, but only the

Fill properties for INDEX: FillFactor and Pad_index

Label:When you create INDEX, you must carefully consider the settings for properties FillFactor and Pad_index, which only work when CREATE INDEX or rebuild index , which represents the index The Fill level of page (Leaf-level or Intermediate-level).

SSH command parsing

Tags: ssh command catOpenSSH is the free version of the SSH Connection tool. Telnet,rlogin and FTP users may not realize that the passwords they transmit on the Internet are unencrypted, but SSH is encrypted and OpenSSH encrypts all communications

s3c2440 ADC (Analog-to-digital converter)

Label:This part of the content is transferred from ZHAOCJ's blog, thanks! Address: http://blog.csdn.net/zhaocj/article/details/5495730  A/D conversion, also known as modulo/number conversion, is the conversion of analog signals into digital signals

Float (floating-point) function detailed

Label:class Float (object):"""Floating point number, float (x)Convert a string or number to a floating point number, if possible."""def as_integer_ratio (self):"" "gets the simplest ratio of the value of the change" """""Float.as_integer_ratio ()

Weak references, soft references, virtual references, and strong references

Label:If an object has only a weak reference to it, the garbage collector reclaims the object immediately, which is an eager way to recycle. In contrast, if there are soft references to these objects, the objects are reclaimed only if the JVM

ASM 32/64

Label:I wrote it using NASM, running on 32-bit Windows and Linux hosts, but later the demand increased and needed to run on 64-bit Windows and Linux, and Windows itself had a WOW (Windows on Windows) mechanism, 32-bit programs can run on 64-bit

About Salt-value encryption

Label:The first time I heard about the value of salt encryption, it always feels strange. Because it is always associated with salty, the association of the password is salty.in fact, the salt mentioned here, simply said, is a set of safe random

How to download the Symhelp tool and use it to collect Sep logs (how to download symhelp tools)

Tags: log logs symantec Sep sepmOs:windows R2SEPM--> 12.1 RU6 MP3SEP--> 12.1 RU6Refer article:About Symantec Help (SYMHELP)Https://support.symantec.com/en_US/article.TECH170735.htmlSymantec Help (SymHelp)

Probe into the Operator of Blender script

Label:Addon (plug-in) is used to extend the functionality of Blende R, as in other software plugin (plug-ins), remove does not affect the operation of the software. Plugins can be added to Blender's user preferences directory, or in the. blend file

Why is the numeric type byte value range ( -128~127)?

Label:Before we solve this problem, we should understand a few concepts.First, the concept of the original code, the inverse code, the complement  The inverse code and the complement of positive numbers are the same as the original code;Negative

Bootstrap List Group Listgroup

Label:List groupsA list group is a new component of the bootstrap framework that can be used to make lists, vertical navigation, and more, as well as to make more beautiful components with other components. Since it is an independent component in

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