INF3703 – STUDY NOTES
(2022).
Chapter 1: Database Systems
Data: Raw facts
Information: The result of processing raw data to reveal its meaning.
Knowledge: The body of information and facts about a specific subject.
Data Management: A discipline that focuses on the proper generation, storage...
Information: The result of processing raw data to reveal its meaning.
Knowledge: The body of information and facts about a specific subject.
Data Management: A discipline that focuses on the proper generation, storage and retrieval
of data.
Database: A shared, integrated computer structure that stores a collection of:
End-user data or raw facts of interest to the end user.
Metadata or data about data, through which the end-user data are integrated and
managed.
DBMS (Database management system): A collection of programs that manage the
database structure and controls access to the data stored in the DB.
Data Inconsistency: Exists when different versions of the same data appear in different
places.
Query: A specific request for data manipulation. Done through the DBMS.
Types of databases
Single User DB: Supports only one user at a time. It runs on a PC and is called a desktop
DB.
Multiuser DB: Supports multiple users at the same time, when it has a small user base it is
called a workgroup DB, if it supports more than 50 users it is called an enterprise DB.
Centralised DB: A DB that supports data located at a single site.
Distributed DB: A DB that supports data distributed across several different sites.
Operational DB: A DB that is designed primarily to supports a company’s day to day
operations. (AKA Transactional DB, Production DB)
Data Warehouse: Focuses on storing data used to generate information required to make
tactical or strategic decisions.
Why DB design is important
DB Design: Refers to the activities that focus on the design of DB structure that will be used
to store and manage end user data.
,Historical Roots: Files and File Systems
Basic file terminology:
Field: A character or group of characters that has a specific meaning. A field is used to
define and store data.
Record: A logically connected set of one or more fields that describe a person, place or
thing.
File: A collection of related records.
Limitations of file system data management:
Requires extensive programming.
There are no ad hoc query capabilities.
System admin can be more complex and difficult.
It’s difficult to make changes to existing structures.
Security features are likely to be inadequate.
Structural and Data dependence:
Structural Dependence: Access to a file is dependent on its structure.
Structural Independence: Exists when it’s possible to make changes in the file structure
without affecting the application program’s ability to access the data.
Data Dependence: Because all data access programs are subject to change when any of
the file’s data storage characteristics change the file system is said to exhibit data
dependence.
Data Independence: Exists when it is possible to make changes in the data storage
characteristics without affecting the application program’s ability to access the data.
The practical significance of data dependence is the difference between the logical data
format (how the human views the data) and the physical data format (how the computer
sees the data). Data dependence makes the file system extremely cumbersome from a
programming and data management point of view.
Data Redundancy
Islands Of Information: The storage of the same basic data in different locations. This
means some variations of the same data can also be saved.
Data Integrity: The condition in which all of the data in the DB are consistent with real world
events and conditions.
Data Redundancy: Exists when the same data are stored unnecessarily at different places.
Uncontrolled data redundancy sets the stage for:
, Data Inconsistency: Exists when the same data are stored unnecessarily at
different places.
Data Anomalies: Occurs when all of the required changes in the redundant data are
not made successfully. Types of anomalies: Update, Insert, Delete.
Database Systems
The database system environment
Fig 1.6 P21 – Contrasting database and file systems.
Database system: Refers to an organization of components that define and regulate the
collection, storage, management and use of data within the DB environment. It is comprised
of 5 parts:
Hardware
Software
People
Procedures
Data
DBMS Functions
A DBMS performs several important functions that guarantee the integrity and consistency of
the data in the DB:
Data Dictionary Management: The DBMS stores definitions of the data element and
their relationships (metadata) in a data dictionary.
Data Storage Management: The DBMS creates and manages the complex
structures required for data storage, thus relieving you of the difficult task of defining
and programming the physical data characteristics.
Data Transformation and Presentation: The DBMS transforms entered data to
conform to required data structures.
Security Management: The DBMS creates a security system that enforces user
security and data privacy.
Multiuser Access Control: The DBMS uses sophisticated algorithms to ensure that
multiple users can access the database concurrently without compromising the
integrity of the DB
Backup and Recovery Management: The DBMS provides backup and data
recovery to ensure data safety and integrity.
Data Integrity Management: The DBMS promotes and enforces integrity rules, thus
minimizing data redundancy and maximizing data consistency.
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