explain various database models in dbms

Explain various database models in DBMS,

Explain database models in DBMS with examples, 

database models in DBMS PDF download

1.The hierarchical model:
2.The network model
3.The relational model (RDBMS)
4.The deductive model
5.The object model (ODBMS)

1.The hierarchical model: 

 

Databases appeared in the late 1960s, at a time when the need for a flexible information management system had arisen. There are five models of DBMS, which are distinguished based on how they represent the data contained:

The hierarchical model: The data is sorted hierarchically, using a downward tree. This model uses pointers to navigate between stored data. It was the first DBMS model.
 
o Also use Records, Links (similar to Network Model)
o Database is collection of rooted trees => forest
 

Hierarchical Model – Tree-Structure Diagrams

Tree-structure diagram (Data-structure diagram)

o No cycle ( arbitrary graph in Network Model)

o Only 1:1 and 1:M can be directly represented

For M: N relationships, we need 2 separate tree structure diagrams.

Hierarchical Model – Sample Database Trees

Hierchical Model – Tree-Structure Diagrams

the following relationships between branch, account, and customer:

we need 2 separate tree-structure diagrams:

 

o To avoid record duplication, use virtual records:

 

2.  The network model:
like the hierarchical model, this model uses pointers toward stored data. However, it does not necessarily use a downward tree structure.

Network Model – Basic Concepts

o Data are represented as collection of records
o Relationships are represented as links
o Each record is a collection of fields:
 
type  customer = record
customer-name: string;
customer-street: string;
customer-city: string;

end
type account = record
account-number: string;
balance: integer;
end

Data-structure diagram:
- Same purpose as an ER diagram.
- Boxes (record types)
- Lines (links)

Many to Many:

 One to many from customer to account:

One to One:

Network Model – Relating 3 Record Types
A customer may have several accounts, each in a specific branch.
An account may belong to several different customers.

A link can connect only 2 record types
=> We need to use a new record type (Rlink) as below:

    3. The relational model (RDBMS, Relational database management system): 

The data is stored in two-dimensional tables (rows and columns). The data is manipulated based on the relational theory of mathematics. 

3. The deductive model: 

Data is represented as a table, but is manipulated using predicate calculus.

4. The object model (ODBMS, object-oriented database management system): 

the data is stored in the form of objects, which are structures called classes that display the data within. The fields are instances of these classes 

By the late 1990s, relational databases were the most commonly used (comprising about three-quarters of all databases).

DBMS various Database model pdf download