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Fifth Normal Form (5NF)

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Release： 2023-09-18 12:45:07
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第五范式 (5NF)

5NF (fifth normal form) is also known as item joining paradigm. If a relation is 4NF, it is in fifth normal form (5NF) and does not losslessly decompose into smaller tables.

You can also consider the relationship to be 5NF if the candidate key is . Every connection dependency in it is implicit.

Example

The following relationship violates normalized fifth normal form (5NF) -

DavidJava E145##JohnJamieEmma##The above relationship can be decomposed into the following three tables; therefore, it is not in 5NF -
EmpName强>

 EmpSkills

 ##EmpJob (Assigned work)

JavaScript

E146

jQuery

E146 td>

p>

Java

E147

 p>

##EmpNameJavaScriptjQueryJava
EmpSkills

David
Java ##John

##Jamie

Emma

##The following are the relationships showing the assignments to Each employee’s job-

td>

##EmpName

EmpJob##David

 E145
John

 E146
Jamie

 E146
Emma

 E147

The following are the skills relevant to the assigned job-

p>

EmpSkills

EmpJob##Java

##Java

 E145
JavaScript

 E146
jQuery

 E146

E147

Our connection dependencies-

{(EmpName, EmpSkills), (EmpName, EmpJob), (EmpSkills, EmpJob)}

The above relationships have connection dependencies properties, so they do not belong to 5NF. This means that the connection relationship of the above three relationships is equal to our original relationship
.

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source：tutorialspoint.com
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