Database Concepts

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Questions:

Generic 3

5 x 3 = 15

Write a note on different types of DBMS users.

Explain Object Model with example.

Explain Cartesian Product with a suitable example.

What is the role of DBA?

What is the difference between Select and Project command?

Generic 5

5 x 5 = 25

Explain the components of DBMS.

Explain the characteristics of DBMS.

Differentiate DBMS and RDBMS.

Explain the different types of relationship mapping.

10.

Explain the different types of data model.

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Answers Key:

Generic 3

5 x 3 = 15

Database Administrators:
Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.
Application Programmers or software Developers:
This user group is involved in developing and designing the parts of DBMS.
End User:
All modern applications, web or mobile, store user data. Applications are programmed in such a way that they collect user data and store the data on DBMS systems running on their server. End users are the one who store, retrieve, update and delete data.
Database designers:
Database designers are responsible for identifying the data to be stored in the database for choosing appropriate structures to represent and store the data.

Object model stores the data in the form of objects, attributes and methods, classes and inheritance. This model handles more complex applications, such as Geographic information System (GIS),sdentific experiments, engineering design and manufacturing. It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.

An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model
(i) Circle has the attribute radius.
(ii) Rectangle has the attributes length and breadth.
(iii) Triangle has the attributes base and height.
(iv) The objects Circle, Rectangle and. Triangle inherit from the object Shape

(i) Cross product is a way of combining two relations. The resulting relation contains, both relations being combined.
(ii) A x B means A times B, where the relation A and B have different attributes.
(iii) This type of operation is helpful to merge columns from two relations

Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.

Select	Project
1. Symbol - σ	1. Symbol - π
2. Selecting a subset with tuples	2. Contains a vertical subset of relation.
3. Select filters out all tuples that don't satisfy the condition.	3. Projection eliminates all attributes of the input relation except in the projection list.

Generic 5

5 x 5 = 25

The Database Management System can be divided into five major components as follows:
(i) Hardware
(ii) Software
(iii) Data
(iv) Procedures / Methods
(v) Database Access Languages

(i) Hardware: The computer, hard disk, I/O channels for data, and any other physical component involved in storage of data
(ii) Software: This main component is a program that controls everything. The DBMS software is capable of understanding the Database Access Languages and interprets into database commands for execution.
(iii) Data: It is that resource for which DBMS is designed. DBMS creation is to store and utilize data.
(iv) Procedures/Methods: They are general instructions to use a database management system such as installation of DBMS, manage databases to take backups, report generation, etc
(v) DataBase Access Languages: They are the languages used to write commands to access, insert, update and delete data stored in any database.
Examples of popular DBMS: Dbase, FoxPro

Characteristics of Database Management System

1. Data stored into Table	Data is never directly stored into the database. Data is stored into tables, created inside the database. DBMS also allows to have relationship between tables which makes the data more meaningful and connected.
2. Reduced Redundancy	In the modern world hard drives are very cheap, but earlier when hard drives were too expensive, unnecessary repetition of data in database was a big problem But DBMS follows Normalisation which divides the data in such a way that repetition is minimum.
3. Date Consistency	On live data, it is being continuously updated and added, maintaining the consistency of data can become a challenge. But DBMS handles it by itself.
4. Support Multiple user and Concurrent Access	DBMS allows multiple users to work on it( update, insert, delete data) at the same time and still manages to maintain the data consistency.
5. Query Language	DBMS provides users with a simple query language, using which data can be easily fetched, inserted, deleted and updated in a database.
6. Security	The DBMS also takes care of the security of data, protecting the data from unauthorized access. In a typical DBMS, we can create user accounts with different access permissions, using which we can easily secure our data by restricting user access.
7. DBMS Supports Transactions	It allows us to better handle and manage data integrity in real world applications where multi-threading is extensively used.

Basis of Comparison	DBMS	RDBMS
Expansion	Database Management System	Relational Database Management System
Data storage	Navigational model ie data by linked records	Relational model (in tables). ie data in tables as row and column
Data redundancy	Exhibit	Not Present
Normalization	Not performed	RDBMS uses normalization to reduce redundancy
Data access	Consumes more time	Faster, compared to DBMS.
Keys and indexes	Does not use.	used to establish relationship. Keys are used in RDBMS.
Transaction management	Inefficient, Error prone and insecure	Efficient and secure
Distributed Databases	Not supported	Supported by RDBMS.
Example	Dbase, FoxPro.	SQL server, Oracle, mysql, MariaDB, SQLite.

Types of relationships:
(i) One-to-One Relationship
(ii) One-to-Many Relationship
(iii) Many-to-One Relationship
(iv) Many-to-Many Relationship
(i) One-to-One Relationship:
In One-to-One Relationship, one entity is related with : only one other entity. One row in a table is linked with only one row in another table and vice versa.
For example: A student can have only one exam number

(ii) One-to-Many Relationship.
In One-to- Many relationship, one entity is related to many other entities. One row in a table A is linked to many rows in a table B, but one row in a table B is linked to only one row in table A.
For example: One Department has many staff members.

(iii) Many-to-One Relationship:
In Manyto- One Relationship, many entities can be related with only one in the other entity.
For example:
A number of staff members working in one Department.
Multiple rows in staff members table is related with only one row in Department table.

(iv) Many-to-Many Relationship:
A manyto- many relationship occurs when multiple records in a table are associated with multiple records in another table.
(i) Example 1:
Customers and Product
Customers can purchase various products and Products can be purchased by many customers
(ii) Example 2:
Students and Courses
A student can register for many Courses and a Course may include many students
(iii) Example 3:
Books and Student.
Many Books in a Library are issued to many students.

10.

Types of a Data Model:
1. Hierarchical Model
2. Relational Model
3. Network Database Model
4. Entity Relationship Model
5. Object Model.
1. Hierarchical Model:
(i) Hierarchical model was developed by IBM as Information Management System. In Hierarchical model, data is represented as a simple tree like structure form.
(ii) This model represents a one-to-many relationship i.e., parent-child relationship. One child can have only one parent but one parent can have many children.
(iii) This model is mainly used in IBM Main Frame computers.

2. Rational Model:
(i) The Relational Database model was first proposed by E.F. Codd in 1970. Nowadays, it is the most widespread data model used for database applications around the world.
(ii) The basic structure of data in relational model is tables (relations). All the information's related to a particular type is stored in rows of that table.
(iii) Hence tables are also known as relations in a relational model. A relation key is an attribute which uniquely identifies a particular tuple (row in a relation (table)).

3. Network Model:
Network database model is an extended form of hierarchical data model. The difference between hierarchical and Network data model is:
(i) In hierarchical model, a child record has only one parent node,
(ii) In a Network model, a child may have many parent nodes. It represents the data in many-to-many relationships.
(iii) This model is easier and faster to access the data.

(iv) School represents the parent node
(v) Library, Office and Staff room is a child to school (parent node)
(vi) Student is a child to library, office and staff room (one to many relationship)
4. Entity Relationship Model:
(i) In this database model, relationship are created by dividing the object into entity and its characteristics into attributes.
(ii) It was developed by Chen in 1976. This model is useful in developing a conceptual design for the database. It is very simple and easy to design logical view of data. The developer can easily understand the system by looking at ER model constructed.
(iii) Rectangle represents the entities. E.g. Doctor and Patient.
(iv) Ellipse represents the attributes E.g. D-id, D-name, P-id, P-name. Attributes describes the characteristics and each entity becomes a major part of the data stored in the database. Diamond represents the relationship in ER diagrams e.g; Doctor diagnosis the Patient.

5. Object Model:
(i) Object model stores the data in the form of objects, attributes and methods, classes and Inheritance.
(ii) This model handles more complex applications, such as Geographic information System (GIS), scientific experiments, engineering design and manufacturing.
(iii) It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.

(iv) An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model.
(i) Circle has the attribute radius.
(ii) Rectangle has the attributes length and breadth.
(iii) Triangle has the attributes base and height.
(iv) The objects Circle, Rectangle and Triangle inherit from the object Shape.