Information Systems (5 ECTS Credits) Diarmuid Ó Muirgheasa BA BAI MIEI

Course Details 5 ECTS Credits Out of total 25 option credits 50% Continual Assessment 10% ERD Assignment 10% DFD in-class exam 5% Data Normalisation Assignment 25% Microsoft Access Project 50% Exam NB: Do NOT assume it will be the same as previous years! Sample paper will be provided 3 hours per week Will be a mix of lectures/tutorials/lab work – we’ll take it week by week, veer more labs towards the end of term

Key Learning Outcomes What is a database? What is it for? Databases in society Data normalisation (/normalization) Identifying Primary Keys and Foreign Keys Data Flow Diagrams (DFDs) Entity Relationship Diagrams (ERDs) Other database-ey stuff… **To give you the skills needed to interact intelligently with software developers, software architects, DBAs, etc etc**

What is a database?

A Database is: A repository of data. More specifically, an electronic system used to store, retrieve and manipulate data

Exercise: Take 3 minutes to compile a list of databases which hold information about you

What are the risk/dangers of having your data stored on these systems?

Risk Associated with Data Breach -Identity theft -Blackmail -Profiling (eg US no-fly list) -Privacy Breach?

Advantages/Disadvantages of DB Approach to Data Management

File Processing Systems Old approach. Not only wasteful of space, but also introduces the near certainty of redundancies and inconsistencies (which DBs mostly solve)

Redundancy The unnecessary (and potentially harmful) duplication of data

Disadvantages of File Processing Systems Lack of Data Independence “Data Independence” – allows us to change the underlying data structure without changing the programs relying on it. (Might seem like a small thing, but in a large organisation nothing would get done if this wasn’t the case!) Lack of support for data integrity Inadequate backup and recovery mechanisms No query language support No support for management of metadata

Disadvantages of Database Systems Cost of software, hardware, training Loss of autonomy – central control of data means there can be a lack of flexibility/control for the developers and users of some applications Inflexibility due to complexity

Data Integrity Consistency and Accuracy of data in DB Data Redundancy is a significant threat Support for data integrity is a key feature of DBMSs DBs model a mini world in which we define many rules, eg: Every student must have exactly one address A diploma can only be issued following completion of 180 ECTS credits A student number must be unique A student date of birth must be at least… Integrity Constraints and Data Validation are key tools here Concurrency Control is also a major issue (mostly beyond the scope of this course)

Structuring Data

College Database – Student Table Student NoNameDoB 1John 2Jane 3Bob

College Database – Student Table Student NoNameDoB 1John 2Jane 3Bob Student Number is a Unique ID

Key Concept: “Primary Key”. Used to uniquely identify a record (“row”) in the database

College Database – Subject Table Need subject name and academic year to identify a row Subject NoSubject NameAcademic YearLecturer 1Econ Milton Friedman 2CompSci Dennis Ritchie 3Econ JB Say OR: We could just use this ID…

Key Concept: “Composite Primary Key”. Primary key made up of multiple fields which together uniquely identify a row

College Database – Enrolment Table EnrolmentIDSubject NameAcademic YearStudent No 1Econ Econ Econ Again, we have the choice of which primary key to use – but we can see that the composite key option is becoming quite complex…

Lab 01 Create tables and relationships as below. Add at least three students, two subjects, and two enrolments per subject. When finished, create a report (using the Report Wizard) that contains the following: Student Number, Student Name, DoB, , Academic Year, Subject Name, Lecturer. Ensure it has a neat layout.