Java Reference
In-Depth Information
Table 1-16: SalesPersons
Salesperson
Vendor
Product
Jones
Acme Widget
Printer
Jones
Acme Widget
Copier
Jones
Zeta Products
Printer
Jones
Zeta Products
Copier
This table contains a certain amount of redundancy, which can be removed by
converting the data to the fifth normal form. Conversion to the fifth normal form is
achieved breaking the table down into smaller tables, as shown in Tables 1 -17 , 1-18 ,
and 1-19 .
Table 1-17: SalesPersons by Vendor
Salesperson
Vendor
Jones
Acme Widget
Jones
Zeta Products
Table 1-18: SalesPersons by Product
Salesperson
Product
Jones
Printer
Jones
Copier
Table 1-19: Products by Vendor
Vendor
Product
Acme Widget
Printer
Acme Widget
Copier
Zeta Products
Printer
Zeta Products
Copier
Boyce-Codd normal form
Boyce-Codd normal form (BCNF) is a more rigorous version of the third normal form
designed to deal with tables containing the following items:
 
Multiple candidate keys
 
Composite candidate keys
 
Candidate keys that overlap
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