Different Database Models Assignment

[Different Database models]
[1]Hierarchical Model
In this type of database model data elements have one-to-many relationships. Hierarchical model
is of tree like structure.
Limitation of this model is many-to-many relationship does not exist.
[2] Network Model
Network model is a type of database model in which data elements implements many to many
relationships.

[3] Relational Model
Relational model is a type of database model in which data entities have a grid like relationship
in the form of columns and rows. Relational model graphically represents the logical relationship
of entities in order to create database.
[4] Data Manipulation language
Data Manipulation language (DML) is a type of computer programming language by which data
is modified, added, deleted in a specified database. It is used to manipulate the data like adding
new elements to the database, retrieving through the database, deleting the unwanted or
redundant data. DML commands are not permanent to database, it can be rolled back.
It has three main commands namely:-
1. INSERT- It is used to insert data into database tables.
Syntax is INSERT into table-name values (data1,data2,..);
Example-
Student_id Student_name Age
INSERT into Student values (420, ‘John’, 20);

Output
Student_id Student_name Age
420 John 20
2. UPDATE- It is used to update a row.
Syntax is UPDATE table-name set column-name = value where condition;
Example Output- UPDATE Student set age=18 where Student_id=420;
Student_id Student_name Age
420 John 18
3. DELETE- This is used to delete data elements from a table.
Syntax is DELETE from table-name;
It can also be used with condition like DELETE from student where Student_id=420;
Student_id Student_name Age
[5] Data Definition Language
Data definition language (DDL) is used to change to structure of database and schema. Mainly
CREATE, ALTER OR DROP commands are used in this language. CREATE command is used
for creating new table; ALTER OR DROP is used to remove a table and its definitions.
Syntax for CREATE- CREATE table-name;
Syntax for ALTER or DROP- ALTER table table-name add (column name, data type);
[6] Data Independence
Data independence is crucial for maintaining the database. Changes in one level doesn’t affect
other level is data independence. There are three levels of database-
1. Physical level
2. Logical level
3. View level
Database independence exits in physical and logical level.

Physical data independence indicates how really information is put away in a database. Changes
made in physical level don't affect the consistent level information.
Logical data independence indicates how information is overseen inside a database. In the event
that a few changes are done, it'll not influence information dwelling in the disk.
[7] Data Redundancy Issues
Data redundancy means multiple storing of same data over different locations. This increases the
storage unnecessarily.
[8] Data integrity
Data integrity in any database is the quality of data that maintains the accuracy and reliability. It
is important to maintain the accuracy throughout the entire life cycle because it is often used by
organization to make decisions.
[9] Schema- It is the logical structure of the database. There are two types of schema-
a. Physical schema- Database design at physical level.
b. Logical schema- Database design at logical level.
Field- A group of characters that has a specific meaning
View- A stored query is called view.
Index- It is a copy of selected data and rows that can be searched very efficiently and it is
additionally an immediate connection for the entire record.
Data Dictionary- It is a crucial part of any database that contains the necessary records, data
ownership and data relationships. Generally it contains the database metadata.

APPROACHES
[1] Top Down
It is the designing of schema in which higher level entity is broken down into two lower level
entities. Generally it is called as specialization process.
Example:
[2] Bottom up
Bottom up is a generalisation process in schema in which two low level entities are combined
into one higher level entity.
Example:

[3] Entity relationships diagram
Entity relationship diagrams shows graphical representation of data elements called entities. It
can be of three types one-to-one, one-to-many, many-to-many.1
ONE-TO-ONE
ONE-TO-MANY
MANY-TO-MANY
[4] Determinacy diagrams
Determinacy diagram shows the dependencies of attributes and the primary key in a graphical
representation. It is a way of examining the relationships between different entities.2
1 Vangie Beal, (2016) entity-relationship diagram (model)
2 Chapter 8. Data Normalisation

Example:
In this example performer-id is the primary key and it is linked to other entities.
[5] Data flow diagrams
Data flow diagrams are a way of graphically representing the flow of data through information
systems describing its designing process. It gives a diagram the whole procedure which can later
be expounded. There are different notations, signs and shapes that wholly describe the steps from
source to destination.3
[6] Entities
An entity is a real world object that can be easily identifiable. It can be vivify or lifeless. For
instance, in a school database, understudies, courses offered and classes all are elements. These
all elements have their characteristics or properties that give them their personality.4
[7] Attribute and Key identifiers
Attribute is a characteristic of one or grouped entities. It shows the properties of entities.
There are many types of key identifiers that are named according to their behaviour. Key
identifiers are used to identify the record. Types of key identifiers are: 5
 Super key- It uniquely identifies each record and is the superset of candidate key.
 Primary key- It is one of the main keys that uniquely identifies each record.
 Foreign key- A key which uniquely identifies record of in other table.
 Candidate key- It can be used as a primary key.
 Composite key- It uniquely identifies entity occurrence.
3 Wikipedia, Data flow diagram
4 ER Model - Basic Concepts
5 Database keys

[8] Functional Dependency
Functional dependency exists when one element of a table is identified by other element within
the table. It database language when one attribute uniquely defines other attribute is called as
functional dependency.
[9] Normal Forms
 First Normal Form- This normal form defines that all the attributes in a relation must
have atomic domains. The values in an atomic domain are invisible units.6
The table below follows the first normal form-
 Second Normal Form- In this every non prime key attribute is fully functionally
dependent on prime key attribute.
6 Normalization of Database

Here, there are two primary keys Stu_ID and Proj_ID and according to the rule,
Stu_name and Proj_name will be dependent on both and not individually.
 Third Normal Form- This form must follow second normal form and satisfy following
conditions: Firstly, No prime key attribute is transitively dependent on prime key
attributes. Secondly, for any non trivial functional dependency X---> A, X is a superkey
and A is a prime attribute.
Example:
Above diagram shows the transitive dependency as city can be identified by Stu_ID and
Zip code both. So break them and we will get-
[New developments]
[1] Dynamic Storage

It is a type of volatile storage that gets vanishes when power is turned off. Best example can be
RAM that loses memory when PC is turned off.
[2] Data Mining and Data Warehousing
Data warehousing is the collection of data which is subject oriented and non-volatile in nature. It
contains all the history of any informational database. It is used by analysts to take better
decisions.
Data Mining is the process of turning raw data into useful information. It is basically digging of
information from data warehouse i.e. database.
[3] Web based database application
A web based database application gives intuitive access to different database information,
tracking and retrieving of information remotely from anywhere. Database applications that can
be accessed and functioned remotely is known as web based database application.7
[4] Document Management System
Document Management System is a storage system that stores different kind of files. It gives the
facility of tracking and managing the stored information. Generally stored information is
electronic documents and images that are saved using document scanner machine. It is integrated
and powerful software that manages all the necessary information.
[5] Digital Libraries
A digital library is a library that stores different multimedia files like texts, images, videos,
electronic documents. It is available on internet or on any other form like CD-ROM. In CD-
ROM it has limited storage while over internet it has enormous amount of space. Depending
upon the purpose, user can store and retrieve the data.8
Works Cited
[1]Beal, V. (2016). https://www.webopedia.com/TERM/E/entity_relationship_diagram.html
[2] Anonynous, 2014.https://www.cs.uct.ac.za/mit_notes/database/htmls/chp08.html
7 Applications Services
8 Margarat Rouse, 2015. digital library

[3]https://en.wikipedia.org/wiki/Data_flow_diagram
[4]https://www.tutorialspoint.com/dbms/er_model_basic_concepts.htm
[5]https://www.studytonight.com/dbms/database-key
[6]http://www.studytonight.com/dbms/database-normalization.php
[7]Anonymous, (2014). http://www.demers-negrete.com/services_application_development.html
[8]Rouse, M. (2015). http://whatis.techtarget.com/definition/digital-library