Module introduction
This module introduces the fundamental concepts of database systems, covering the definition, structure, and organization of data. Students will learn about database queries and gain proficiency with SQL through practical examples. The course will also explore the historical development of databases, the advantages of using databases, and detailed discussions on data integrity and independence. Key topics include standard architectures, user roles, and administrative tasks. Assessments will involve coursework on database creation and SQL queries.
Module introduction
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Presentation Transcript
Module introduction INF08104: Database Systems Brian Davison, 2011/12
Agenda • What is a database? • Module structure • Organising data • Simple queries • SQLzoo
What is a database? • A model of some real-world situation • A business tool • A technical solution • A valuable asset • A large organised collection of data
A little bit of history • Pre-1950: Negligible electronic data storage • 1950 – 1970: Application of computing to standard data problems • 1970: Edgar Codd, A Relational Model of Data for Large Shared Data Banks • 1970 – 1985: Massive growth in relational database use • 1985 – 2011: Experimentation with object-orientation, digital objects, etc.
The database approach Table name = EMP Schema Data
Database advantages • Data independence • Multi-user access • Data integration • Data integrity • Enforcement of standards • Security • Performance
Data integrity • Type checks • e.g. ensuring a numeric field is numeric and not a character • Redundancy checks • direct or indirect - this check is not automatic in most cases and must be added by the database designer • Range checks • e.g. to ensure a data item value falls within a specified range of values, such as checking dates so that say (age > 0 AND age < 110). • Comparison checks • in this check a function of a set of data item values is compared against a function of another set of data item values. For example, the max salary for a given set of employees must be less than the min salary for the set of employees on a higher salary scale.
Roles • End users • Application programmers • Database administrator
Module structure • Theory • Standard architecture, security, concurrency • Design • Analysis, schema definition, diagrams • Use • SQL, embedded SQL • Administration • Backup & recovery, user management, scripting
Assessment • Coursework 40% • Details in week 4 • Database creation • SQL queries • Deadline week 9 – 1200, Friday 4th November • Exam 60% • Theory • SQL queries
Let’s organise some data! • Four volunteers • What are they? • What data could we store about them?
Entities and attributes Student Name Phone number Gender Date of birth Course
Entity = STUDENT Attributes Tuple
COUNTRY Entity = Attributes Tuples
Talking to the database • Which records? • Europe • Which columns? • Name • Population
Talking to the database SQL = Structured Query Language SELECT <column names> FROM <table name> WHERE <criteria> Which columns Which records
Query example SELECT name, population FROM country WHERE region = 'Europe'
All columns SELECT * FROM countries WHERE region = 'Europe'
More than one condition SELECT name FROM countries WHERE region = 'Europe' AND name LIKE 'A%'
Ordering the results SELECT name FROM country WHERE region = 'Europe' • AND name LIKE 'A%' ORDER BY name
Your turn • You are a telephone company preparing your customers’ monthly bills. • Write a query to identify each customer and their Internet use for last month. The table name is USAGE
SELECT customer_id, gb FROM usage WHERE month = May AND year = 2011 Why is this wrong?
SELECT customer_id, gb FROM usage WHERE month = 'May' AND year = 2011 Solution
Your turn again • You are a university library. • Suggest a query to identify the borrowers with late items. • The name of the table is LOAN • For today's date, use TODAY
SELECT borrower_id FROM loan WHERE due_date < TODAY AND status = 'on loan' Solution
