Learn about Data Base Models

<span style="font-weight:bold;">Database Models. </span>

<span style="font-weight:bold;">Q1. Define Database model?</span>

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

<span style="font-weight:bold;">Q2. Describe the different models in DBMS?</span>

   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

<span style="font-weight:bold;">Q4. Define Data abstraction?</span>

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

 
<span style="font-weight:bold;">
Q4. Define the degree of abstraction?</span>

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.
                  
                  

<span style="font-weight:bold;">Q5. Define Transaction?</span>

    * 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.

 
 
<span style="font-weight:bold;">
Q6. How many levels are there to access the data?</span>

    * 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.

 
 
<span style="font-weight:bold;">
Q7. Define Entity and attributes?</span>

    * 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.

 
 
<span style="font-weight:bold;">
Q8. Define Identifiers?</span>

    * Identifiers are used to uniquely identify each entity instance.

 
 
<span style="font-weight:bold;">
Q9. Define Relationship in E-R Diagram?</span>

    * 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.