2. DATA MODELS
INTRODUCTION
• A Data Model is a set of concepts that can be used
to describe the structure of data in a database.
• A database model shows the logical structure of a
database, including the relationships and constraints
that determine how data can be stored and
accessed.
• Data Models are used to support the development of
information systems by providing the definition and
format of data to be involved in future systems.
• Data model also gives idea about possible alternatives
to achieve targeted solution.
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4. HIERARCHICAL MODEL
• This model is developed by IBM and North American
Rockwell Known as Information Management System.
• This is the oldest and simplest DBMS model.
• The model is sorted hierarchical ,either in top down or
bottom up approach of designing.
• This model uses pointers to navigate between stored
data.
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6. BUSINESS RULE
• One parent node can have many child nodes ,but
one child cannot have more than one parent.
• Relationship is one to many.
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7. ADVANTAGES OF
HIERARCHICAL MODEL
Conceptual
Relationship between various level
is logically very simple. Hence
database structure becomes easier
to view.
Database Security
Security is given by DBMS system
itself.
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8. • Simple creation ,Updation and Access
• This model is simple to construct with help of pointers .
• Easy to understand .
• Easy to delete and add records in the database using pointers .
• This is faster and easy data retrival through higher level records in
tree structure.
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9. • Database Integrity
• There is parent child association
between different levels of records in
files.
• Child record is attached with the parent
record which maintains the integrity
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10. • Efficiency
• This model having good performance when
database contains large amount of data in which
one record has many related records like a class
contains many students studying in it.
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11. DISADVANTAGES OF
HIERARCHICAL MODEL
Complex
Programmers and designers need
to have knowledge of physical
data storage which may be
complex.
Difficult to manage
Any change in a location of data
needs change in all application
programs that accesses changes
data.
Data access is restricted by pointer
path.
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12. • Limitations in implementation
• It is difficult to implement many to
many relationship.
• Query optimization is not possible or
possible up to certain extent.
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13. NETWORK MODEL
• This model is similar to Hierarchical
model, this model also uses pointers
toward data but there is no need of
parent to child association .
• It uses graph data structure.
• A child can have more than one parent.
• It has one to many or many to many
relationship.
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14. • A relationship between any two record types is called as
a set.
• Data in network model are represented by
collectionof records and relationships among data are
represented by links, which can be viewed as pointers.
• The records in the database are organized as
collection of arbitrary groups.
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16. ADVANTAGES OF
NETWORK MODEL
Simple design
The network model is simple and easy to
design and understand.
Ability to handle many types
relationship
The network model can handle the one
to many or many to many or other
relationships.
Hence network model manages
multiuser environment.
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17. • In a network model, an application can
access a root(parent) record and all the
member records within a SET (child).
• Provide very efficient and high speed
• retrieval.
Ease of
data
access
• In a network model, no member can exist
• without a parent entity.
• A user must first define the root record
and
• then the child record.
Data
Integrity
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18. • Data Independence
• In network model, application
programs work independently of the
data.
• Any changes made in the data do not
affect the application programs.
• In a network model ,administrators
offer data creation by DDL and DML.
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19. DISADVANTAGES OF NETWORK MODEL
System Complexity
In a network model ,data are accessed one
record at a time.
This can increase the complexity of system
for accessing multiple records at a time.
Lack of structural
Any changes made to the database
structure require the application programs
to be modified before it can access data.
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20. RELATIONAL MODEL
• The Relational Model is first proposed by E.F
Codd.
• This model uses collection of tables to represent relationships
amongst the data.
• In this model ,each database item is viewed as a record with
attributes. A set of records with similar attributes is called a
TABLE. Each table contains a record of a particular type.
• The database uses Relational model called as
RDBMS .
• A Relational database is a collection of 2-D tables
which consist of rows and columns.
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21. • Relational model is the most popular model and the
most extensively used model.
• In this model the data can be stored in the “tables” and this
storing is called as “relation”, the relations can be normalized
and the normalized relation values are called atomic values.
• Each row in a relation contains unique value and it is called as
“tuple”, each column contains value from same domain and it
is called as “attribute”.
• Most of the popular commercial DBMS products like Oracle,
Sybase , MySQL, are based on relational model.
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22. • A particular attribute or combination of attributes is chosen as a
primary key that can be referred to in other tables, when it’s called
a foreign key.
• The model also accounts for the types of relationships between
those tables, including one-to-one, one-to-many, and many-to-
many relationships.
• Within the database, tables can be normalized that make the
database flexible, adaptable, and scalable. When normalized, each
piece of data is atomic, or broken into the smallest useful pieces.
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24. ADVANTAGES OF RELATIONAL MODEL
1. Relational Algebra
• A relational database supports relational
algebra and also relational operations of the
set theory like union , intersection
,difference , cartisen product , relational
database also support select , project ,
join and division operations.
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25. • Dynamic Views
• In a RDBMS , a view is not a part of the physical schema , it is always
dynamic.
• Structured query language (SQL)
• For data access in RDBMS we have query language SQL .Most of the
database vendors support the SQL standards.
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26. 4. Excellent data security
• Relational databases support the concept of
user rights, every user is assigned with some
database permission called as user rights.
• Relational databases are scalable and provide
good support for the implementation of
distributed systems and other advanced
database systems.
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