DBMS Redundancy control scheme

1. NORMALIZATION &
TYPES
S.Manju
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2. Agenda
 Normalization
 Why Normalization ?
 Properties
 1 NF
 2 NF
 3 NF
 BCNF
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3. Normalization
&
Why
Normalization?
 Decomposition of fat relations into smaller meaningful relations
 Higher the normal forms higher the number of relations and
higher the quality of data
 To minimize redundancy
 To minimize insertion, deletion and updation anomalies
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4. Ethics of
Normalization
Lossless Join ( Non Additive Join Property)
 Assures no spurious table generation
 Assures no loss of records
R = R1  R2
R = R1 (r) Join R2 (r)
Dependency Preservation Property
 FD’s in Original scheme should exist in decomposed relation as
well
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5. FIRST NORMAL FORM
 Attribute values must be atomic or single or indivisible
 A relational schema R is in first normal form if the domains of all attributes of R are atomic
 R:
 R1 R2
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EID ENAME ELOC
EID ENAME EID ELOC

6. SECOND NORMAL FORM
 A relational schema R is in second normal form if Relation R is in
 1 NF
 All non prime attributes in the table must be fully functionally dependent on the primary
key.
 R:
 R1 R2
 R3
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EID ENAME ELOC PID PHRS
EID ENAME EID ELOC
EID PID PHRS

7. FULL & PARTIAL FUNCTIONAL DEPENDENCIES
 An FD X->Y is PFD if,
 Removal of an attribute from X still holds the dependency
 Eg : Eid,Pid -> Ename (PFD)
 Hence Decompose !
 An FD X->Y is FFD if,
 Removal of an attribute from X breaks the dependency
 All attributes has major contribution
 Eid,Pid->Phrs (FFD)
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8. THIRD NORMAL FORM
 A relational schema R is in third normal form if Relation R ,
 is in 2 NF
 No non prime attribute of R is transitively dependent on primary key of R
 R :
 Eid ->Ename, Dob, Did, Dname
 Did->Dname
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EID ENAME DOB DID DNAME

9. THIRD NORMAL FORM
 Transitive dependency
 Eid->Did ,Did->Dname and hence Eid->Ename exists !
 Transitive Dependency exists ! Hence Decompose !
 Decomposed tables,
 R1 R2
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EID ENAME DOB DID DID DNAME

10. BCNF NORMAL FORM
 Very stricter version of 3 NF
 A relational schema R is in Boyce codd normal form if Relation R ,
 is in 3 NF
 For every non trivial FD X->A , X must be a super key !
 R :
 Eid ->Ename, Dob, Did
 Did->Dname
 Eid and Did { Super Keys }
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EID ENAME DOB DID DNAME

11. THANKYOU !
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