Database 1

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Database Systems Design, Implementation, and Management

Coronel | Morris

11e

Chapter 1

Database Systems

Learning Objectives

In this chapter, you will learn:
The difference between data and information
What a database is, the various types of databases, and why they are valuable assets for decision making
The importance of database design
How modern databases evolved from file systems

Learning Objectives

In this chapter, you will learn:
About flaws in file system data management
The main components of the database system
The main functions of a database management system (DBMS)

Data vs. Information

Data

Information

Raw facts
Raw data - Not yet been processed to reveal the meaning
Building blocks of information
Data management
Generation, storage, and retrieval of data

Produced by processing data
Reveals the meaning of data
Enables knowledge creation
Should be accurate, relevant, and timely to enable good decision making

Database

Shared, integrated computer structure that stores a collection of:
End-user data - Raw facts of interest to end user
Metadata: Data about data, which the end-user data are integrated and managed
Describe data characteristics and relationships
Database management system (DBMS)
Collection of programs
Manages the database structure
Controls access to data stored in the database

Role of the DBMS

Intermediary between the user and the database
Enables data to be shared
Presents the end user with an integrated view of the data
Receives and translates application requests into operations required to fulfill the requests
Hides database’s internal complexity from the application programs and users

Figure 1.2 - The DBMS Manages the Interaction between the End User and the Database

Advantages of the DBMS

Better data integration and less data inconsistency

Data inconsistency: Different versions of the same data appear in different places

Increased end-user productivity

Improved:

Data sharing
Data security
Data access
Decision making
Data quality: Promoting accuracy, validity, and timeliness of data

Types of Databases

Single-user database: Supports one user at a time
Desktop database: Runs on PC
Multiuser database: Supports multiple users at the same time
Workgroup databases: Supports a small number of users or a specific department
Enterprise database: Supports many users across many departments

Types of Databases

Centralized database: Data is located at a single site
Distributed database: Data is distributed across different sites
Cloud database: Created and maintained using cloud data services that provide defined performance measures for the database

Types of Databases

General-purpose databases: Contains a wide variety of data used in multiple disciplines
Discipline-specific databases: Contains data focused on specific subject areas

Types of Databases

Operational database: Designed to support a company’s day-to-day operations
Analytical database: Stores historical data and business metrics used exclusively for tactical or strategic decision making
Data warehouse: Stores data in a format optimized for decision support

Types of Databases

Online analytical processing (OLAP)
Enable retrieving, processing, and modeling data from the data warehouse
Business intelligence: Captures and processes business data to generate information that support decision making

Types of Databases

Unstructured data: It exists in their original state
Structured data: It results from formatting
Structure is applied based on type of processing to be performed
Semistructured data: Processed to some extent
Extensible Markup Language (XML)
Represents data elements in textual format

Database Design

Focuses on the design of the database structure that will be used to store and manage end-user data
Well-designed database
Facilitates data management
Generates accurate and valuable information
Poorly designed database causes difficult-to-trace errors

Evolution of File System Data Processing

Table 1.2 - Basic File Terminology

Figure1.6 - A Simple File System

Problems with File System Data Processing

Structural and Data Dependence

Structural dependence: Access to a file is dependent on its own structure
All file system programs are modified to conform to a new file structure
Structural independence: File structure is changed without affecting the application’s ability to access the data

Structural and Data Dependence

Data dependence
Data access changes when data storage characteristics change
Data independence
Data storage characteristics is changed without affecting the program’s ability to access the data
Practical significance of data dependence is difference between logical and physical format

Data Redundancy

Unnecessarily storing same data at different places
Islands of information: Scattered data locations
Increases the probability of having different versions of the same data

Data Redundancy Implications

Poor data security
Data inconsistency
Increased likelihood of data-entry errors when complex entries are made in different files
Data anomaly: Develops when not all of the required changes in the redundant data are made successfully

Types of Data Anomaly

Lack of Design and Data-Modeling Skills

Evident despite the availability of multiple personal productivity tools being available
Data-modeling skills is vital in the data design process
Good data modeling facilitates communication between the designer, user, and the developer

Database Systems

Logically related data stored in a single logical data repository
Physically distributed among multiple storage facilities

DBMS eliminates most of file system’s problems

Current generation DBMS software:

Stores data structures, relationships between structures, and access paths

Defines, stores, and manages all access paths and components

Figure 1.8 - Contrasting Database and �File Systems

Figure 1.9 - The Database System Environment

DBMS Functions

Data dictionary management

Data storage management

Data transformation and presentation

Security management

Data dictionary: Stores definitions of the data elements and their relationships

Performance tuning: Ensures efficient performance of the database in terms of storage and access speed

Transforms entered data to conform to required data structures

Enforces user security and data privacy

DBMS Functions

Multiuser access control

Backup and recovery management

Data integrity management

Sophisticated algorithms ensure that multiple users can access the database concurrently without compromising its integrity

Enables recovery of the database after a failure

Minimizes redundancy and maximizes consistency

DBMS Functions

Database access languages and application programming interfaces

Database communication interfaces

Query language: Lets the user specify what must be done without having to specify how
Structured Query Language (SQL): De facto query language and data access standard supported by the majority of DBMS vendors

Accept end-user requests via multiple, different network environments

Disadvantages of Database Systems

Table 1.3 - Database Career Opportunities