database normalization using dependencies graph fotache_m_strimbei_c__ibima2008

Marin Fotache, Catalin StrimbeiIBIMA2008

Back to Simplicity: An Old-Looking New Database Design

Methodology

An “ancient” problemHow to design a database schema for a real-

world application ?Modeling, analysis & design approaches

E/RUnified Process (UML)Agile methodologiesEtc

Normalization

Two methodologies of Normalization

Decomposition (Codd, 1972 & co)Splitting repeatedly the Universal Relation

into relations in order to remove partial and transitive functional dependencies, multivalued and join dependencies

1NF 2NF 3NF BCNF 4NF 5NF...

Synthesis (Bernstein, 1976)

The proposed guide - pillars

Keeping some repeating groups and splitting the others

Functional dependenciesRemoving simmetrical FD’sUsing surrogate keys for:

Identification problemsTransforming MVDs

Inclusion dependencies (IS-A roles)Graphical representation

A FD chart (graph)

A simplified version of the chart

Representing Inclusion Dependencies

Comparison

Surrogation for “fixing” the chart

A “hard surrogation” case

Accepting insular attributes

BCNF transformation

BCNF transformation - example

Trick and surrogates

(Another) Trouble with FDs

A FD/IND based solution

MVD’s – (a R.Fagin’s example)

Emp#

SpouseID

ChildID

Year

SalaryHireDate

EmpDept

PersNameYearOfBirth

Removing MVDs – two solutions