范式图形辨析-Mysql Tutorial-php.cn

Home

Database

Mysql Tutorial

范式图形辨析

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 07, 2016 pm 04:06 PM

graphicsSummarizeparadigmsolve

首先用一句话总结要辨析的5中范式分别解决的问题： 1NF：属性原子性 2NF:部分依赖 3NF：传递依赖（非主属性对关键码） BCNF：传递依赖（主属性对候选键） 4NF：（最高级别的范式，不常用这里引用定义）D是R上成立的FD和MVD集合，并且D中每个非平法的X→→Y的

首先用一句话总结要辨析的5中范式分别解决的问题：

1NF：属性原子性

2NF:部分依赖

3NF：传递依赖（非主属性对关键码）

BCNF：传递依赖（主属性对候选键）

4NF：（最高级别的范式，不常用这里引用定义）D是R上成立的FD和MVD集合，并且D中每个非平法的X→→Y的左部X都是R的超键

其中第一范式，画图省略。第四范式不常用画图省略。

2NF如下：

3NF:

BCNF：喎?http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHA+PGltZyBzcmM9"http://www.2cto.com/uploadfile/Collfiles/20141022/2014102209204921.jpg" alt="\">

至于4NF，我现在还不是太清楚，请大侠指教。但是其他的范式，我自我感觉理解还可以，若有不懂的朋友可以点击右上角的“Q我吧”一起探讨~

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

MySQL String Types: Storage, Performance, and Best PracticesMay 10, 2025 am 12:02 AM

MySQLstringtypesimpactstorageandperformanceasfollows:1)CHARisfixed-length,alwaysusingthesamestoragespace,whichcanbefasterbutlessspace-efficient.2)VARCHARisvariable-length,morespace-efficientbutpotentiallyslower.3)TEXTisforlargetext,storedoutsiderows,

Understanding MySQL String Types: VARCHAR, TEXT, CHAR, and MoreMay 10, 2025 am 12:02 AM

MySQLstringtypesincludeVARCHAR,TEXT,CHAR,ENUM,andSET.1)VARCHARisversatileforvariable-lengthstringsuptoaspecifiedlimit.2)TEXTisidealforlargetextstoragewithoutadefinedlength.3)CHARisfixed-length,suitableforconsistentdatalikecodes.4)ENUMenforcesdatainte

What are the String Data Types in MySQL?May 10, 2025 am 12:01 AM

MySQLoffersvariousstringdatatypes:1)CHARforfixed-lengthstrings,2)VARCHARforvariable-lengthtext,3)BINARYandVARBINARYforbinarydata,4)BLOBandTEXTforlargedata,and5)ENUMandSETforcontrolledinput.Eachtypehasspecificusesandperformancecharacteristics,sochoose

How to Grant Permissions to New MySQL UsersMay 09, 2025 am 12:16 AM

TograntpermissionstonewMySQLusers,followthesesteps:1)AccessMySQLasauserwithsufficientprivileges,2)CreateanewuserwiththeCREATEUSERcommand,3)UsetheGRANTcommandtospecifypermissionslikeSELECT,INSERT,UPDATE,orALLPRIVILEGESonspecificdatabasesortables,and4)

How to Add Users in MySQL: A Step-by-Step GuideMay 09, 2025 am 12:14 AM

ToaddusersinMySQLeffectivelyandsecurely,followthesesteps:1)UsetheCREATEUSERstatementtoaddanewuser,specifyingthehostandastrongpassword.2)GrantnecessaryprivilegesusingtheGRANTstatement,adheringtotheprincipleofleastprivilege.3)Implementsecuritymeasuresl

MySQL: Adding a new user with complex permissionsMay 09, 2025 am 12:09 AM

ToaddanewuserwithcomplexpermissionsinMySQL,followthesesteps:1)CreatetheuserwithCREATEUSER'newuser'@'localhost'IDENTIFIEDBY'password';.2)Grantreadaccesstoalltablesin'mydatabase'withGRANTSELECTONmydatabase.TO'newuser'@'localhost';.3)Grantwriteaccessto'

MySQL: String Data Types and CollationsMay 09, 2025 am 12:08 AM

The string data types in MySQL include CHAR, VARCHAR, BINARY, VARBINARY, BLOB, and TEXT. The collations determine the comparison and sorting of strings. 1.CHAR is suitable for fixed-length strings, VARCHAR is suitable for variable-length strings. 2.BINARY and VARBINARY are used for binary data, and BLOB and TEXT are used for large object data. 3. Sorting rules such as utf8mb4_unicode_ci ignores upper and lower case and is suitable for user names; utf8mb4_bin is case sensitive and is suitable for fields that require precise comparison.

MySQL: What length should I use for VARCHARs?May 09, 2025 am 12:06 AM

The best MySQLVARCHAR column length selection should be based on data analysis, consider future growth, evaluate performance impacts, and character set requirements. 1) Analyze the data to determine typical lengths; 2) Reserve future expansion space; 3) Pay attention to the impact of large lengths on performance; 4) Consider the impact of character sets on storage. Through these steps, the efficiency and scalability of the database can be optimized.

See all articles

Hot AI Tools

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress images for free

Clothoff.io

AI clothes remover

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

How to fix KB5055523 fails to install in Windows 11?

4 weeks agoByDDD

How to fix KB5055518 fails to install in Windows 10?

4 weeks agoByDDD

Roblox: Grow A Garden - Complete Mutation Guide

3 weeks agoByDDD

Roblox: Bubble Gum Simulator Infinity - How To Get And Use Royal Keys

3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

How to fix KB5055612 fails to install in Windows 10?

3 weeks agoByDDD

Hot Tools

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software