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Transcript
Databases and modelling 1. day Agenda • Goals • Plan • What is database? • How is database developed and designed? • Database design 2 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 3 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. 4 Course plan – this week • Monday:10.15-12: 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) 5 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 6 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 7 What is a database? • Hierarchical databases – e.g. windows file system • Relational databases – e.g. MS Access, the focus of this course 8 Relational databases • User Interface – data in & out (Reports) (Forms and queries) • Data: Tables and relations 9 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? 10 Step 1-2 11 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… 12 Step 3 13 Example 14 Data design Use 10-15 minutes to start designing your data To begin with, list the data you want to find in the database Distinguish between entities (usually nouns in a narrative about the system), their attributes and relations (look for verbs in the narrative) 15 Step 4 16 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: Make the database smaller Make data input easier Make search easier 17 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. 18 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. 19 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. 20 Entity-relation diagram Entity Attribute Relationship Cardinality – what kind of relation? •One to one •One to many •Many to many •Many to one 21 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. 22