Databases and modelling 1. day

2 Agenda Goals Plan What is database? How is database developed and designed? Database design

3 Databases and modelling Goal: That you can model and implement a small database Form: Mix of lectures and exercises Design task:Construction of a litterature database

4 Formalities The module is concluded by an internal written individual test in: IT technology: Databases. The test takes the form of a set take-home assignment to be handed in after 3 days, in which the student completes a designated task on data modelling, SQL, and modelling and search tools, thus documenting his/her command of the techniques covered in the course. A grade according to the 7-point grading scale is given. In relation to the competence goals stipulated in section 8 of the study regulation the test documents the student’s ability to: choose the form of and execute data modelling on a limited set of data define suitable search functions for the above reflect on own practice and document the reflection.

5 Course plan – this week Monday: : Introduction to databases – data analysis and modelling Tuesday 9-12: Design of database tables and relations Wednesday 9-12: Design of database user interface, design of queries and forms, introduction to SQL Thursday: Database implementation (without teacher) Friday: Database implementation (without teacher)

6 Course plan – next week Monday: 9-12 Introduction to CMS and portfolio, Typo3 basics Tuesday: 9-12 Typo3 basics Wednesday: Portfolio implementation continued and reflection (without teacher). Thursday: Portfolio implementation continued and reflection (without teacher). Friday: 9-11 Presentation of portfolio, database and reflections week 36-37

7 What is a database? A database is a collection of logically related data designed to meet the information needs of one or more users. Wikipedia

8 What is a database? Hierarchical databases – e.g. windows file system Relational databases – e.g. MS Access, the focus of this course

9 Relational databases User Interface – data in & out (Reports) (Forms and queries) Data: Tables and relations

10 Methodology Start with the goal – what do you want? What do you want to be able to find in the database? What must the database as a consequense of the above contain?

11 Step 1-2

12 For now… Just be creative – there is so many ways to find and express the goal of a database and some of them are covered by the other courses. Use 5-10 minutes to decide what you want to be your goal in designing a database for data about the stuff you read and learn. On to data analysis and design…

13 Step 3

14 Example

15 Data design Use minutes to start designing your data BTo begin with, list the data you want to find in the database BDistinguish between entities (usually nouns in a narrative about the system), their attributes and relations (look for verbs in the narrative)

16 Step 4

17 Table design From data to formal description of tables and relations The database stores data in tables with relations to each other 3 normal forms The principles for normal forms and normalization explains the need for relations – but said in a simpler way the database is split in more tables to: BMake the database smaller BMake data input easier BMake search easier

18 1. Normal form All table entries must be of equal length. The table must not contain repeating entries or groups Example: In a litterature database the author must be placed in an individual table – otherwise entries would be of different length depending on number of authors.

19 2. Normal form Give all tables a primary key (tables created to handle relations can have a primary key). Make separate tables for each attribute shared between many entities.

20 3. normalform Entries in a table must not be functionally dependent of each other – only of the primary key. Example: A database does not have employe ID and name in the same table – unless one of them is primary key.

21 Entity-relation diagram Attribute Relationship Entity Cardinality – what kind of relation? One to one One to many Many to many Many to one

22 Design database Use an entity-relation diagram to document the table design you want to implement Browse chapter one Browse the next chapters about Access.