Fifth normal form in Database management system | Normalization and its type

FIFTH NORMAL FORM-

DEFINITION- A table is in fifth normal form (5NF) or Project-Join Normal Form (PJNF) if
1. It is in 4NF 
2. It cannot have a lossless decomposition into any number of smaller tables. 

EXAMPLE- Consider a relation as an example of a buying table.This is used to track buyers, what they buy, and from whom they buy.

Buyer	Vendor	Item
Sally	Liz Claiborne	Blouses
Mary	Liz Claiborne	Blouses
Sally	Jordach	Jeans
Mary	Jordach	Jeans
Sally	Jordach	Sneakers

Problem:- The problem with the above table structure is that if Claiborne starts to sell Jeans then how many records must you create to record this fact? The problem is there are pair wise cyclical dependencies in the primary key. That is, in order to determine the item you must know the buyer and vendor, and to determine the vendor you must know the buyer and the item, and finally to know the buyer you must know the vendor and the item.

Solution:- The solution is to break this one table into three tables; Buyer-Vendor, Buyer-Item, and Vendor-Item. So following tables are in the 5NF.

Relation Buyer-Vendor-

Buyer	vendor
Sally	Liz Claiborne
Mary	Liz Claiborne
Sally	Jordach
Mary	Jordach

Relation Buyer-Item-

Buyer	Item
Sally	Blouses
Mary	Blouses
Sally	Jeans
Mary	Jeans
Sally	Sneakers

Relation Vendor-Item-

Vendor	Item
Liz Claiborne	Blouses
Jordach	Jeans
Jordach	Sneakers

These relation are in 5NF.