Slide 1
Data Base NormalizationBy Prof. ManikandanDept of Computer
ApplicationQMC College, [email protected]
NormalizationA logical design method which minimizes data
redundancy and reduces design flaws.to improve storage efficiency,
data integrity, and scalability. The normal forms break down large
tables into smaller subsets.
Goal: - Eliminate redundant data in a DB. - Ensure data
dependencies make sense.
Normalization BenefitsFacilitates data integration.Reduces data
redundancy.Provides a robust architecture for retrievingand
maintaining data.Compliments data modeling.Reduces the chances of
data anomaliesoccurring.DBMS KeysPrimary Key: Uniquely identify
records from the same table. Avoid duplicate values.
Foreign Keys: An attribute or a set of attributes of one table
that is matched to candidate keys of another table (or even the
same table). That is, a child table may reference the parent table
for appropriate attribute values.
Candidate Keys: A minimal set of attributes in a table that
uniquely identifies a record.When there is more than one attribute
in the candidate key, it is called composite key.Normal
FormsNormalization works through a series of stages called normal
forms:First normal form (1NF)Second normal form (2NF)Third normal
form (3NF)Boyce Codd normal form (BCNF)The highest level of
normalization is not always desirable.First Normal Form (1NF)Each
attribute must be atomicNo repeating columns within a row.No
multi-valued columns.
1NF simplifies attributesQueries become easier.
First Normal Form (1NF)
Second Normal Form (2NF)Each attribute must be functionally
dependent on the primary key. Functional dependencies are the
relationships among the attributes within a relation.the property
of one or more attributes that uniquely determines the value of
other attributes.Any non-dependent attributes are moved into a
smaller (subset) table.2NF improves data integrity. Prevents
update, insert, and delete anomalies.
Functional Dependence
Name, dept_no, and dept_name are functionally dependent on
emp_no. (emp_no -> name, dept_no, dept_name) Skills is not
functionally dependent on emp_no since it is not unique to each
emp_no.
Second Normal Form (2NF)
Third Normal Form (3NF)Transitive Dependencies:Is A Relationship
Between Attributes Such That The Values Of One Attribute Is
Dependent On, Or Determined By, The Values Of Another Attribute
Which Is Not A Part Of The Key.Third Normal Form (3NF)Remove
transitive dependencies.Transitive dependence - two separate
entities exist within one table.Any transitive dependencies are
moved into a smaller (subset) table.
3NF further improves data integrity.Prevents update, insert, and
delete anomalies.
Transitive Dependence
Dept_no and dept_name are functionally dependent on emp_no
however, department can be considered a separate entity.Third
Normal Form (3NF)
Boyce-Codd Normal Form (BCNF)A relation is in BCNF if and only
if every determinant is a candidate key. Notes: BCNF is a stronger
form of 3NF BCNF => 3NF 3NF > BCNF
Violation of BCNF happen under specific conditions: A relation
contains two (or more) composite candidate keys, which overlap and
share at least one attribute in common.
SUMMARY
Normalization Process
Converting to a class diagram to normalized table
One to many relationship
Supplier(SID, Name, Address, City, State, Zip,
Phone)Employee(EID, Name, Salary, Address, )
The many side becomes a key (underlined). Each PO has one
supplier and employee.(Do not key SID or EID)Each supplier can
receive many POs. (Key PO)Each employee can place many POs. (Key
PO)One to many relationship sample data
Many to many relationship
Each POID can have many Items (key/underline ItemID).Each ItemID
can be on many POIDs (key POID).N-Ary associations
Thank you..
