Important Computer Awareness Materials for IBPS Exams 2017 (Day-9)

Important Computer Awareness for IBPS Exams 2017 (Day-9) – DBMS Part-9:

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Types of Data Models:

1. Object based data models

(a) ER Data models

(b) Object oriented data models

2. Physical Models

3. Record Based Data models

(a) Hierarchical Data Models

(b) Network Data models

1. Object based data models:

(A) ER data models:

ER data model is the representation of real world objects with their attributes and relationship.

Rectangles are used to represent the entity in the diagram. Name of the Entity is written inside the rectangle.

A strong entity is represented by simple rectangle as shown above. A weak entity is represented by two rectangles as shown below.

Attribute:

An oval shape is used to represent the attributes. Name of the attribute is written inside the oval shape and is connected to its entity by a line.

Multivalued attributes are represented by double oval shape; whereas derived attributes are represented by oval shape with dashed lines. A composite attribute is also represented by oval shape, but these attribute will be connected to its parent attribute forming a tree structure.

Primary key:

An underline to the attribute name is put to represent the primary key. The key attribute of the weak entity is represented by dashed underline.

Relationship:

A diamond shape is used to show the relationship between the entities. A mapping with weak entity is shown using double diamond. Relationship name will be written inside them.

One to one relation:

A one-to-one relationship is represented by adding ‘1’ near the entities on the line joining the relation. In another type of notation one dash is added to the relationship line at both ends.

One to many relation:

A one-to-many relationship is represented by adding ‘1’ near the entity at left hand side of relation and ‘N’ is written near the entity at right side. Other type of notation will have dash at LHS of relation and three arrow kind of lines at the RHS of relation as shown below.

Many to many relation:

A one-to-many relationship is represented by adding ‘M’ near the entity at left hand side of relation and ‘N’ is written near the entity at right side. Other type of notation will have three arrow kinds of lines at both sides of relation as shown below.

(B) Object oriented data model:

An object database (also object-oriented database management system, OODBMS) is a database management system in which information is represented in the form of objects as used in object-oriented programming. Object databases are different from relational databases which are table-oriented. Object-Relational database are a hybrid of both approaches