Database Some walk through lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 1.

Præsentationer af emnet: "Database Some walk through lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 1."— Præsentationens transcript:

1 Database Some walk through lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 1

2 Database Design – Begreber 1 Database: En fælles samling af logiske relaterede data (informationer) DBMS (database management system) Et SW system der gør det muligt at definer, oprette og vedligeholde Databaser Applications program Et program der interagere med databasen View Et udtræk fra databasen til en bruger, der er logget ind – Findes ikke i databasen lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 2

3 lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 3 Functions For a DBMS #1 Data storage, retrieval and update A user-accessible catalogue Transaction support Concurrency control services Recovery services

4 lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 4 Functions For a DBMS #2 Authorization services Support for data communication Integrity services Services to promote data independence Utility services

5 Database – not a single system lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 5

6 MS-SQL – Architecture

7

8 Database – Process organisation

9 Databases - system and user

10 Exercise – What is a Database Review Questions (book chapter 1 p.20)  1.2 + 1.4 + 1.6 Reflect upon the questions  1.5 + 1.7 + 1.8 lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 10

11 lv/09-2008 Figures & some text from: © Pearson Education Limited 1995, 2005 11 DBMS: ANSI-SPARC

12 Example

13 lv/09-2008 Figures & some text from: © Pearson Education Limited 1995, 2005 13 Description of the 3 levels #1 External Level – Users’ view of the database. – Describes that part of database that is relevant to a particular user. Conceptual Level – Community view of the database. – Describes what data is stored in database and relationships among the data.

14 lv/09-2008 Figures & some text from: © Pearson Education Limited 1995, 2005 14 Description of the 3 levels #2 Internal Level – Physical representation of the database on the computer. – Describes how the data is stored in the database.

15 DataBase Modelling You will model – Conceptual schema (Tables, Constraints, Procedures etc.) – External schema (Views) Modelling takes its base from – Class Diagram (Domain Model or model-part of Design Class Diagram) – ER Diagram (DB diagram tool to show Entity-Relationship) lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 15

16 Database Design – Begreber 2 Relationel model Relation (Table, Entity) inf. med søjler (column) og rækker (row) Attribute (column) Tuple (Række, Record) Domain (MS sql = User Defined Data Types) Tilladte værdier for en attribut (fx. 1-50) lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 16

17 Database Design – Begreber 3 Nøgler Super key (Samling søljer til at udpege en række) Candidate key (Minimum af søljer til at udpege en række) Primary key (Valg af en kandidat nøgle) Foreign key (Søljer til en sammenhæng til en anden tabel) lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 17

18 Database Design – Begreber 4 Integrity Entity Integrity (The table itself is well defined i.e primary key (+ normalisation) ) Referential Integrity (The foreign key has something to point to in primary table) lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 18

19 Exercise – What is Relation Model Review Questions (book chapter 2 p.35-36)  2.1 + 2.3 + 2.4 + 2.5 lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 19

20 Entity integritet - Normalisering What could happen? (figure 8.2) – Insert anormalitet – Delete anormalitet – Update anormalitet Hvordan – NF1: primær nøgle + kun én værdi i hver ‘celle’ – NF2: NF1 + del af primær nøgle IKKE alene udpege andre felter i rækken – NF3: NF2 + kun primær nøgle udpege felter i rækken

21 lv/02-2015 Figures & some text from: © Pearson Education Limited 1995, 2005 21 Insert -> insert new member => branch information insert new branch => no staff information Deletion -> delete ‘Art Peters’ => delete branch! Modification -> modify telNo for branch for Tom => remember for sally!

22 Entity integritet - Normalisering How -> Normal Forms (NF) – 1NF: primær nøgle + kun én værdi i hver ‘celle’ Eks: flere telefon numre -> løsn = ny tabel – 2NF: 1NF + del af primær nøgle IKKE alene udpege andre felter i rækken (functional dependency) Eks: staffNo udpeger navn + posistion = ny tabel – 3NF: 2NF + kun primær nøgle udpege felter i rækken (transitively dependency) Eks: Postnummer postby => ny tabel

23 Refential Integritet Ved fremmed nøgler – afhænger af modellen – Ved delete eller (update) Default Null Cascade No Action