Learn about Data Base Models

Database Models.

Q1. Define Database model?

* A database model is a collection of logical constructs used to represent the data structure and the data relationship found with in the database.

Q2. Describe the different models in DBMS?

1. Hierarchical model:-

o Use to manage large amount of data.
o Its basic logical structure is represented by tree.
o Hierarchical structure contains levels or segments.
o Its advantages are simplicity, Database security, Data independence, Data integrity, Efficiency.
o Its disadvantages are Complex implementation, Difficult to manage, Implementation limitation, Lack structural independence.

2. Network model:-

o The network model was created to represent complex data relationship more effectively.
o The network model aloe to have more than one parent of a child.

3. Relation model:-

o The relational model produced on automatic transmission database to replace the standard transmission.
o The relational data model is implemented through RDBMS.

4. Objected Oriented model:-

o Data and there relationship are contained in a single structure known as object.
o Object oriented data model reflects a very different way to define and use entities

Q4. Define Data abstraction?

* Data abstraction is a mechanism to provide the main feature without describing its background details.

Q4. Define the degree of abstraction?

Ans. There are four models come in degree of abstraction:-

* External model: - 1) End user view.

2) External schema.

* Conceptual model: - 1) Global view of entire database.

2) Integrate all external views.

3) Logical design.

4) Software independence and hardware independence.

* Internal model: - 1) Representation of data as seen by the

DBMS.

2) When ever you change the internal model without affecting the conceptual model then you have logical independence.

* Physical model:- 1) Physical model describe the way data a

are stored in Storage media.

2) that is definition of physical storage device.

3) The access method.

Q5. Define Transaction?

* Transaction is a sequence of operation perfumes as a single logical unit of work.
* A logical unit of work must exhibits four properties i.e. ACID
* A- Atomicity.
* C- Consistency.
* I- Isolation.
* D- Durability.

Q6. How many levels are there to access the data?

* There are three levels to access the data in formatting form:-

1. Physical level: - Physical levels tell how data stored and how access the data.
2. Logical level: - Logical level tells that what we stored in the database.
3. View level: - This level of abstract exists to simplify the interaction with the system.

Q7. Define Entity and attributes?

* Entity: - Entity is an object and generally entity is represented by a table name.
* Attribute: - Attribute is a characteristic of an entity and shown by an Oval shape.

Q8. Define Identifiers?

* Identifiers are used to uniquely identify each entity instance.

Q9. Define Relationship in E-R Diagram?

* A relationship is an association between entities.
* Entities that participate in a relationship are known as participants.

DBMS, Database model, Data abstraction, E-R Diagram, Entity, Attributes, Transaction, Hierarchical model, Network model, Relation model, Objected Oriented model.