Features of database management system

2017

Features of Database Management System

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Task1 Analyse the key issues and application of databases within organizational environments The needs of management and organizations are ever changing, still they are required to be met. There are external pressures from security agencies, taxing authorities, legislators making privacy laws. Such external and internal factors demand organizations to exercise control over their data sources.

All levels of people in organization query from the database for information to conduct daily operations. Database are vital for day to day decision making, planning, control, operations and the management process.

Database management system are designed to manage large amount of information. Examples of large database systems are – Airline reservation systems, banking systems, Automated Teller Machine, Company Payroll System, Staff Management System, Material Management System.

Database systems are designed to provide safety of the stored information, from unauthorized access and system crashes.

One of the major database property is Database Abstraction. As many of the database users are not computer literate, system ensures to provide only relevant data to them, and hides unnecessary details ( like how data is stored ) from them. This makes functionality of the entire organisation simple and user friendly.

Here is a list of four major factors describing why ‘Click Money’ should use databases to improve its day to day operations – 1.

2.

3.

4.

Management of databases help businesses to keep a track of their clients along with their preferences and buying patterns. To automate the financial advice provided to clients. E.g. – By looking at the databases we can find out which chocolates are always purchased, which hotels are frequently booked etc. [Read about Database Key Issues Assignment.]

To maintain details of suppliers, manufacturers, staff To maintain product inventory and shipment tracking To store data of various branches of click money at a centralized location and to access them online

Task 2 General Features of Database Management Systems www.programmingassignmentshelp.net

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The main purpose of database management system is to maintain data integrity in the system. But a good database management system has some other features as well – 1.

Data Definition Language – These are set of commands used to define database schema. E.g. –

     

RENAME ALTER DELETE DROP TRUNCATE CREATE

2.

Data Manipulation Language – These commands manage schema definition. E.g.-

   

SELECT INSERT UPDATE DELETE

3.

Data Dictionary and metadata – A data dictionary is a database repository or a store where metadata resides. A metadata is data about data.

A data dictionary contains:

 

Description of database users and their access permissions Schema, database mapping, constraints

4.

Indexing of data – It is a technique of retrieving data from database based on a value upon which indexing is done. E.g. – All records with name = ‘A’ must be fetched

5.

Instances and Schema – Data within the database keeps on changing with time as it is frequently updated, modified, deleted. This information at any particular point of time is called an instance.

The overall design of database is called schema. E.g. – There are three fields in table ‘Student’ – Student id, Student Roll No, Student Class. The values within these fields are instances and the type of fields (Integer, varchar, nvarchar) in this table is the schema.

Advantages of Database Management Systems: 1.

Controlling Data Redundancy-The data is recorded at only one place in a database and is distinct. E.g. – Dean’s faculty file and Faculty payroll file are two sets of data which have multiple similar entries. When these are converted into a database, the data is integrated such that redundancy is removed and only one record is kept.

2.

Data Consistency –If a data item appears once in a database, its value must be updated only once and as soon as this is done, it must be made available to users. The database management system automatically updates each occurrence of a data item in a database.

3.

Data Sharing –Many users can access same set of data / database simultaneously, as database administrator can give access rights to various users within organisation. Similarly, same database can be shared by multiple application programs.

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4.

Data Integration –One database can contain multiple tables with multiple rows and columns and multiple relationships among tables.

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Task 3 Database Developmental Methodology Structured Systems Analysis and Design method (SSADM) is a set of standard for system analysis and design used for computing projects in United Kingdom.

It uses combination of 3 techniques:

  

Logical Data Modelling – It is the process of identifying, modelling, documenting the data (entity & relationships) requirements of the system.

Data Flow Modelling – It is the process of identifying, modelling, documenting the flow of data within information system.

Entity Behaviour Modelling – It is the identification, modelling and documentation of events that affect each entity and the sequence in which these events occur.

These system models are cross referenced against each other, thus ensuring the accuracy and completeness of entire application.

SSADM application projects can be divided into 5 developmental stages – 1.

2.

        3.

4.

Feasibility Study-It is conducted to determine whether a system can be built within the defined budget or not. It can be divided in two parts – Problem definition and problem identification.

Requirements Analysis – In this phase the requirements of the system to be developed are identified, with the process and data structures involved. Data Flow Diagrams (DFD) are created.

Diagrams of new systems are made including the security requirements of new system. We can explain this DFD in a number of simple steps: Supplier supplies products to the company, which is Click Money.

Company (Click Money) has multiple branches across various cities.

Click Money manages the database of all the branches at one centralized location.

Branches in turn manages all their info and provide to Click Money centralized server.

Click Money has many customers. It sells its financial products to customers and receives service charges from them.

Click Money Database manages all the relevant info of all the customers.

Click Money has staff, whose records are maintained in database server.

Staff salary and Attendance status is to be managed by Click Money Database.

Requirements Specification – All the functional and non functional requirements are identified in detail in this phase.

Logical System Specification – In this phase system design is updated logically and technically.

Refer ER Diagram below.

Task 4 www.programmingassignmentshelp.net

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ER Diagram Entity Relationship Diagram for Click Money Database

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[This is how to Develop a Database Management System Assignment.]

Various Entities, Attributes, Constraints that we see in this E-R Diagram are –In this E-R diagram we can see that: Various ‘Suppliers’ supplies to ‘Company’ (Click Money). ‘Company’ has many ‘branches’. Branches can be Head Office, Regional office or Sub Offices. Company sells various ‘products’ which are supplied by suppliers. ‘Customers’ buys those products. ‘Staff’ works for Company. Company also keeps track of the staff ‘attendance’.

1

2

Entity

Attributes

Constraints

Supplier

Supp_id

Primary Key

Supp_fname

Not Null

Supp_fname

Not Null

Supp_phone

Not Null

Product_id

Foreign key

Supp_Street

Not Null

Supp_City

Not Null

Comp_id

Primary Key

Comp_fname

Not Null

Comp_lname

Not Null

Comp_phone

Not Null

Company

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3

4

5

Branch

Product

Staff

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Comp_street

Not Null

Comp_city

Not Null

Branch_id

Primary Key

Branch_fname

Not Null

Branch_lname

Not Null

Branch_phone

Not Null

Branch_street

Not Null

Branch_city

Not Null

Prod_id

Primary Key

Prod_name

Not Null

Supplier_id

Foreign Key

Staff_id

Primary Key

Staff_fname

Not Null

Staff_fname

Not Null

Staff_salary

Not Null

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6

Attendance (Weak entity set)

Staff_phone

Not Null

Staff_street

Not Null

Staff_city

Not Null

Staff_id

Staff_fname

Primary Key

Staff_lname

Status

Not Null

Various relationships that exist in the above Entity Relationship diagram for Click Money are: Relation Type

Entity Class

Entity Class

Cardinality Ratio

Supplies

supplier

Company

Many to one

Has

company

Branches

One to many

Sells

company

Product

One to many

buys

customer

Product

One to many

Works for

staff

Company

Many to one

Keep track

company

Attendance

One to one

Consider the above entity relationship diagram, we find that there are entities with attributes and relationships with cardinality ratio defined in this diagram.

Here cardinality is essentially the mapping of associated entities in the relationship.

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Types of cardinality are: 1.

2.

3.

4.

One to one (1:1) – E.g. – An employee works for a company, there exists a unique employee and unique company One to many (1: n) – E.g. – One Staff member sells many products Many to One (n: 1) – E.g. – Manufacturer supplies many products to one supplier Many to many (m: n) – E.g. – Many projects can be assigned to many employees

Read more about Computer network Assignment help Normalization – This schema is normalized up to 3NF (Third Normal Form). Each cells of table have single value of attribute. Hence it is following 1 NF, there is no partial or transitive dependency. Every relation is uniquely defined, hence it is also following 2NF and 3 NF (PRAKASH, prashant, 2012).

Task 5 Relational Data Model Tables with corresponding attributes and constraints – 1.

Supplier – Supp_id (PK), Supp_fname, Supp_lname Supp_phone, Product_id (FK), Supp_street, Supp_city

2.

Branch–Branch_id (PK), Branch_fname, Branch_city, Company_id (FK)

3.

Product – Product_id (PK), Product_name, Supplier_id (FK)

4.

Customer – Cust_id (PK), Cust_fname, Cust_lname, Cust_phone, Cust_street, Cust_city

5.

Staff – Staff_id (PK), Staff_fname, Staff_lname, Staff_salary, Staff_phone, Staff_street, Staff_city

6.

Attendance – Staff_id, Staff_fname, Staff_lname, Status (In this table, two candidate keys i.e Staff_id + Staff_fname + Staff_lname are together used to form a primary key)

7.

Company – Comp_city

Comp_id(PK),

Comp_fname,

Branch_lname,

Comp_lname,

Branch_phone,

Comp_phone,

Branch_street,

Comp_street,

Above database schema shows all the tables of Click Money database with their primary and foreign keys.

Click Money Database screenshot using MS Access:

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Above screenshot shows a table relationship diagram for Click Money Database in MS Access.

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Above diagram shows the Customer Details interface of Click Money. By clicking the button we can navigate across the records of database.

Normalization: There is no partial or transitive dependency, every relation is uniquely defined. Relations are having single attribute for a key. Hence the database schema is following 1NF, 2NF, 3NF. Read more about Computer Programming Assignment Help ===========================================================

Task 6 Please refer MS access database, which shows following things: 1.

2.

3.

The necessary constraints, and the appropriate relationships Database tables with sample records A functioning front end user interface that will suit client’s requirements.E.g. – Forms are created wherever necessary.

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References:    

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AZHAR, muhammad. (n.d). What Is Data Dictionary In Dbms? [online]. [Accessed 1 july 2014].

Available from World Wide Web: <http://technology.blurtit.com/756573/what-is-datadictionary-in-dbms> BURNS, joe. 2014. To Use or Not to Use a Database? That is the Question. HTMLGOODIES, (n.d.) (n.d.), p.1.

DATE, C. J. 2000. Introduction to database systems(7th edition).

2004. What are the difference between DDL, DML and DCL commands? [online]. [Accessed 1 july 2014]. Available from World Wide Web: <http://www.orafaq.com/faq/what_are_the_difference_between_ddl_dml_and_dcl_com mands> PRAKASH, prashant. 2012. Basics of Normalization with examples. [online]. [Accessed 1 july 2014]. Available from World Wide Web: <http://www.aliencoders.com/content/basicsnormalization-examples> PURBA, sanjiv. 2000. High-Performance Web Database. CRC press.

SILBERSCHATZ, Abraham, henry F. KORTH, and S. SUDARS. 2006. DATABASE SYSTEMS CONCEPTS. Mcgraw-Hill Higher Education.

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