creating the two tables in the 4NF

Normalization

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NORMALIZATION

Fifth Normal Form (5NF)

These relations still have a problem. While defining the 4NF we mentioned that all the attributes depend upon each other. While creating the two tables in the 4NF, although we have preserved the dependencies between Vendor Code and Item code in the first table and Vendor Code and Item code in the second table, we have lost the relationship between Item Code and Project No. If there were a primary key then this loss of dependency would not have occurred. In order to revive this relationship we must add a new table like the following. Please note that during the entire process of normalization, this is the only step where a new table is created by joining two attributes, rather than splitting them into separate tables.

Project No. Item Code
P1 11
P1 12
P2 11
P3 11
P3 13

Let us finally summarize the normalization steps we have discussed so far.

Input Relation Transformation Output Relation
All Relations Eliminate variable length record. Remove multi-attribute lines in table. 1NF
1NF Relation Remove dependency of non-key attributes on part of a multi-attribute key. 2NF
2NF Remove dependency of non-key attributes on other non-key attributes. 3NF
3NF Remove dependency of an attribute of a multi attribute key on an attribute of another (overlapping) multi-attribute key. BCNF
BCNF Remove more than one independent multi-valued dependency from relation by splitting relation. 4NF
4NF Add one relation relating attributes with multi-valued dependency. 5NF

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