Chapter 11 - Database

Data is important information in computer system nowadays. Database is exist for collection of integrated data. It is logically related files and records.

• Data redundancy – many organizations have multiple files on the same subject or person (for example, records for the same customer may appear in different files across multiple departments)
• Data integrity – accurate updating of files

Two ways to view data :

• Physical view- actual format and location (very specialized computer professionals are concerned with the physical view)
• Logical view - focuses on the meaning and content of the data (end users and most computer professionals are concerned with logical view)

Data Organization - From less complex to more complex : 

• character – basic logical data element

           example : a single letter, number, or special character such as a punctuation mark

• field – next higher level, a group of related characters

           example : a data field which show description or characteristic of an entity (person, place, thing or object)

• record – a collection of related data field 
• table – a collection of related records
• database – is an integrated collection of logically related tables

Key field 

• unique identifier (primary key) to help locate data based on specific requests and each record can be distinguished from any other
• Used to integrate data and helps with finding records, sorting records, compiling information contained in the database

Two main ways to process data :   

1.   Batch processing

• data collected and stored over time, several hours, days or even weeks, then process data later all at one time  as a “batch”
• Example : Bank credit card billing

2.   Real-time processing

• online processing - access data quickly
• Occurs when data is processed at the same time the transaction occurs 
• Made possible by disk packs and direct access storage devices

The difference of batch processing and real-time processing is batch processing store data in a longer time and process data later at once only. But real-time processing access data quickly which the transaction and processing data are occur at the same time - now.

Database Management System

• Nodes - points connected like branches of an upside-down tree
• One parent per node
• If parent node is deleted, all the child nodes are deleted
• New parent node must be created before adding new child node

Five common data models :

1.   Hierarchical database : Parent can have several child nodes (one-to-many relationship)

2.   Network database : Each child node may have more than one parent node (many-to-many relationship)

3.   Relational database : relational data table (via key field)

4.   Multidimensional database : Data Cube

• Used for efficiently analyzed complex data
• Conceptualization – provide users with an intuitive model in which complex data and relationships can be conceptualized
• Processing speed – faster analyzing and querying a large multidimensional database

5.   Object-oriented database

• Objects contain both data and instructions
• Organize using objects, classes, entities, attributes, and methods

The advantages of using a database are :

• Databases offer great opportunities for productivity
• Sharing – information in one department can readily be shared with others in one organization
• Security – Users are given passwords to access the kind of information they need only
• Less data redundancy – decrease of unnecessary duplication of data when several departments use the same database of information
• Increased data integrity - Reduced likelihood of inconsistent, incomplete or inaccurate data

Examples of available databases :

• Business directories
• Demographic data
• Business statistical information
• Text databases
• Web databases

Security is important for database because for an organization, the database of their customers, their information of departments and other important databases is private. Database must be secure to avoid using of database without permission and reveal of important data information. Security may include armed guards to electronic verification of person through fingerprints or eye imaging. Security also can be done by encrypted the database management system and users can be access by enter password. Firewalls are often used by companies to control access to their internal networks.

Kindly refer to the presentation slide which attached in the comment. It shows the example of data management system.