INFO20003 Database Systems
Dr Renata Borovica-Gajic
Lecture 01
What are Database Systems?
INFO20003 Database Systems
Week 1
1
Data vs Information
• Data
– known facts stored and recorded
– can include: text, numbers, dates, plus images, sound, video, and other complex objects
• Information
– Datapresentedincontext(canbesummariseddata)
– Datathathasbeenprocessedincreasingtheusersknowledge
• Data vs Information
– Data is known and available; Information is processed and more useful
Baker, Kenneth D. Doyle, Joan E. Finkle, Clive R. Lewis, John C. McFerran, Debra R. Sisneros, Michael
324917628 476193248 548429344 551742186 409723145 392416582
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Information: data in context
Database Systems Assignment 4 Marks Semester 3 2014
Student Name
Student ID
Grade
Baker, Kenneth D.
324917628
H1
Doyle, Joan E.
476193248
H2B
Finkle, Clive R.
548429344
H3
Lewis, John C.
551742186
H2A
McFerran, Debra R.
409723145
P
Sisneros, Michael
392416582
H3
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Information: Summarisation!
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Course
Tutorial
Name
Metadata – Data about data
Name
Type
Alphanum
Integer
Alphanum
Length
30
2
30
Description
Course ID
Tutorial number
Student name
• Can include:
– structure, rules, constraints
• Why do we need Metadata?
– Consistency – Meaning
• We generate a data dictionary as part of the analysis of system requirements
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What is a “database” ?
a large, integrated, structured collection of data
• Usually intended to model some real-world enterprise
• Example: a university
– Entities … such as courses, students, professors – Relationships … such as enrollment, teaching
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What Is a Database System?
A Database Management System (DBMS) is a software system designed to store, manage, and facilitate access to databases.
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File Processing Systems
• What are the problems you can see with this?
• (Diagram adapted from Hoffer p. 42)
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What’s Wrong Here?
• Program-data dependence
– If the file structure changes, so does the program
– What if you change data structure for one program
• Duplication of data
– wasteful, inefficient, loss of data integrity
• Limited data sharing
– data tied to application, hard/slow to create adhoc reports
• Lengthy development times
– application has to do low level data management, figure out file format each time
• Excessive program maintenance
– up to 80% of development time in traditional file based organisations is for maintenance
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Database Systems as Solution
• •
Manage data in a structured way
Many models (hierarchical, network, etc), but relational
dominant since ~1980
• Relational Model
–Rows & Columns forming Relations –Keys & Foreign Keys to link Relations
Enrolled
Students
sid
cid
grade
53666 53666
53650 53666
Carnatic101 Reggae203
Topology112 History105
5
5.5
6 5
sid
name
login
age
gpa
53666
53688
53650
Jones Smith Smith
jones@cs smith@eecs smith@math
18 18 19
5.4 4.2 4.8
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Database Advantages
• Data independence
– separation of data and program, application logic – central data repository, central management
• Minimal data redundancy
– redundancy can be controlled (normalization)
• Improved data consistency
– single store: no disagreements, update problems, less storage space
• Improved data sharing
– data is shared, a corporate resource, not a necessity for an application – external users can be allowed access
– multiple views of data, arbitrary views of data
• Reduced program maintenance
– data structure can change without application data changing
• Novel ad hoc data access ‘without programming’ – SQL
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–
What’s Examinable?
• Difference between Data and Information
• Being able to discuss the advantages of Databases vs File
Processing Systems
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Next Lecture
• The database system lifecycle
– With a focus on the design stage
• Conceptual design
• Logical design
• Physical design
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