1. Distributed Database Management System
Lecture 6

2. First Three Normal Forms
First Normal Form
Second Normal Form: we are not much interested in it. Its more of a historical perspective
Third Normal Form: 3NF, for each XY where Y is not in X, either X is a superkey of R or Y is prime attribute
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3. Boyce-Code Normal Form
BCNF, For every FD X  Y in R, X is the superkey
Removal of second part creates situation where a relation in in 3NF but not in BCNF, vice versa never happens
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A relation R defined on attributes A(A1, A2, …., An), if XA, YA, ZA, if for each value of X, there is a unique value of (Y,Z) pair and Z depends only on X then X multidetermines Z, X > Z and also X > Y
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Fourth Normal Form
If a relation is in BCNF and all MVDs are also FDs
EMP-PROJ is broken in
EMP(eNo, pNo)
SKILL(eNo, eSkill)
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P-J Dependency
A relation R defined on attributes A(A1, A2, …., An), if XA, YA, ZA, if R is equal to join of X, Y and Z then (X, Y, Z) constitute project-join dependency for R
A relation R is in 5NF if every join dependency is implied by the CKs of R
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Integrity Rules
Rules to maintain the consistency of DB
Structural, Behavioral
Beh: help to capture semantics of App
Should be verified at each update, since updates can lead to inconsistencies
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