CH1 Database system

Chapter 1Database Systems

DatabaseSystemsRob &Coronel

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Database Systems: Design, Implementation, and Management

Database Systems: Design, Implementation, and Management

CHAPTER 1

Database Systems



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Chapter ObjectivesChapter Objectives

Data management problems associated with a file system

Advantages of using a database over a file system

Functions of a database management system



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File TerminologiesFile Terminologies

Table 1.2 Basic File Terminology

Data “Raw” facts that have little meaning unless they have been organized in some logical manner. The smallest piece of data that can be “recognized” by the computer is a single character. Example: the letter A, the number 5, symbols: ‘ ? > * +.

Field A character or group of characters (alphabetic or numeric) that has a specific meaning. Example: Student Name, GPA, ID

Record A logically connected set of one or more fields that describes a person, place, or thing. For example, a student’s record may comprise of his/her name, address, phone number, date of birth, class, GPA, and so on.

File A collection of related records. For example, a file might contain the records for all students currently enrolled at UTA.



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A File System ExampleA File System Example



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File System CritiqueFile System Critique

File System Data Management File systems require extensive programming in 3GL. As file systems become more complex, managing

files gets more difficult. Security features are difficult to implement and are

lacking. Changing requirements mandate changes in existing

file structures. Programs accessing a file are subject to change

when the file structure changes - More maintenance.



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Structural and Data Dependence Structural Dependence

A change in any file’s structure requires the modification of all programs using that file.

Example:

Data DependenceA change in any file’s data characteristics requires changes of all data access programs.

Example:

Logical Vs. physical view of data Structural and data dependence make file systems

very difficult to manage - High Maintenance.



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Data Redundancy:The same information is stored in more than one place.

Example: Problems due to uncontrolled data redundancy

Data Inconsistency (lack of data integrity) Example:

Data anomalies Modification anomalies (Inconsistent data due to

modifications). Example: Insertion anomalies (Inconsistent data due to insertions)

Example: Deletion anomalies (Inconsistent data due to deletions)

Example:



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Example- Data RedundancyExample- Data Redundancy



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Example- Data RedundancyExample- Data Redundancy



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Eliminating Redundant DataEliminating Redundant Data



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Database SystemsDatabase Systems

The database represents a change in the way end user data are stored, accessed, and managed.

Logically related data are stored in a single data repository called a database.

The database contains end-user data and metadata. A DBMS is a collection of programs that manages

the database structure and controls access to the data stored in the database.

DBMS makes it easier to eliminate most of the file system’s data inconsistency, data anomalies, and data and structural dependence problems.



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The Database System Components Hardware

Computer Peripherals

Software Operating systems software DBMS software Applications programs and utilities software



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The Database System Components People

Systems administrators: Database administrators Database designers Systems analysts and programmers End users

Procedures Instructions and rules that govern the design and use of the

database system

Data Collection of facts stored in the database



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Types of Databases Number of Users

Single-user Multi-user

Scope Desktop (Single user) Workgroup (Used by a department, nbr of users < 50) Enterprise (Used by the entire organization, users in 100s)



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Types of Databases Location

Centralized (Database located in a single site) Distributed (Database distributed across multiple sites)

Use Transactional (aka Production)

Supports a company’s day-to-day operations Data integrity and operational efficiency are important

Data warehouse Stores historical, aggregated data Used for managerial decision making – strategic and tactical



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DBMS Functions Data Dictionary Management

Data dictionary stores definitions of the data elements and their relationships (metadata).

It removes structural and data dependency from the system.

Data Storage Management DBMS creates data storage structure and relieves the

programmer from the task of defining and programming physical data characteristics.



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DBMS Functions Data Transformation and Presentation

DBMS transforms data from its logical format to its physical format and vice versa.

Security Management DBMS provides user security and data privacy within the

database. Data security is especially important in multi-user

databases.



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DBMS Functions Multi-User Access Control

DBMS ensures that multiple users can access the database concurrently and still guarantees the integrity of the database.

Backup and Recovery Management DBMS provides backup and recovery procedures to ensure

data safety and integrity.

Data Integrity Management DBMS promotes and enforces integrity rules to eliminate

data integrity problems. Ensuring data integrity is especially important in

transaction-oriented database systems.



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DBMS Functions Database Access Languages & Application

Programming Interfaces The DBMS’s non procedural query language simplifies

data access Data Definition Language (DDL) is used to define the

database structure Data Manipulation Language (DML) is used for accessing

and manipulating data DBMS also provides interfaces to application programs

written in procedural languages such as COBOL, C etc.



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DBMS Functions Database Communication Interfaces

DBMS provides communication interfaces so that the database can be accessed through a network

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CH1 Database system