Database 1: 6 9 2005 08:30 10:30

1
Database 1 6 / 9 / 2005 0830 1030

• Andra Waagmeester

2
Aim of this course

• Introduction to  databases .
• Design and development.
• Be able to cope with every database environment.
• To be able assess and suggest an appropriate
  database environment

3
How will we achieve this

• Lectures
• Skills
•  Fundamentals of Database systems 

4
What is a database

• ?

5
Databases

•  A database is a collection of related data 
• i.e.
• A database represents some aspect of the real
  world (Miniworld or Universe of discourse).
  Changes to the mini world are reflected in the
  database
• A database is a logically cherent collection of
  data with some inherent meaning
• A database is designed, built, and populated with
  data for a specific purpose. It has an intended
  group of users and some preconceived applications
  in which these users are interested.

6
What is a database?

• ?

7
Examples
8
Examples
9
Examples
10
Examples
11
Databases

• Traditional databases
• Multimedia databases
• Geographical databases
• Content management systems
• Reservation systems
• .

12
A little history

• Data stored in the application itself
• Queries in programming code itself
• User and developer same person
• Relational databases (1980 -gt)
• Object orriented databases(1980 -gt)
• World Wide Web -gt (1994 -gt)

13
Who are actors in the database world
14
Database actors

• Social actors
• Database administrator
• Database user
• System analist and programmers
• End user
• Standaard gebruiker
• Gevorderde gebruiker
• Gast gebruiker

15
Database actors

• Technical actors
• Designers and programmers
• Interface and tool designers
• Maintenance personel

16
The file approach

• The data is stored in a file.
• Custom made software is needed
• Advantage Fast and efficient
• Disadvantage Data on multiple places at the same
  time
• Disadvantage Each change in the database
  requires the involvement of a programmer
• Nadeel Data exchange is difficult

17
DBMS
18
The database approach

• Database Management Software (DBMS)
• A DBMS stores both the data and the describtion
  of the data

19
The database approach

• Data-abstraction
• Changing storage, does not require change of
  dbms.
• Operations can be performed.
• Conceptual representation of data (data model)

20
DBMS

• Multiple viewpoints
• Different users have different rights, different
  views and different needs with respect to the
  data in the database

21
Advantages DBMS

• Controlling redundancy
• Efficiency in storage
• Easy adaptation
• Prevention of errors (inconsistency)
• Restricting Unauthorized Access
• User management (passwords / rechten)
• Logging (audit log)
• Backup

22
Advantages DBMS

• Multiple user environments at the same time
• Front-ends
• GUIs
• WWW access
• Application servers

23
Adventages DBMS

• Storage of complex data relationships
• (integrity constraints)
• Which data is allowed
• Which data is allowed
• Automatic edit

24
Effects of DBMS

• Standarization
• RAD
• Flexibility
• Scalability

25
Choices
Money
Time
Quality
26
Pause
27
Deel 2 Concepts en architecture

• Datamodels
• Database schemes
• Database languages
• Interfaces
• Database architecture
• Classification of database systems

28
A datamodel
29
Data-models

• A collection of concepts that can be used to
  describe the structure of a database.

30
Data-models

• Conceptual (high-level) versus
• Usually the level seen by the users / analisten
• Physical (low-level)
• How the data is stored
• In between Representational (implementation)
  data model

31
Conceptual datamodel

• Consists of
• Entities
• Attributes
• Relations
• Entity-relation scheme (Tomorrow)

32
Representational model

• Relational datamodel
• Networkmodel
• Hierarchical model
• Objectmodel

33
Conceptual level
34
Physical model
35
Representational model
36
Scheme (intensiom)

• The description of a database is called the
  database scheme
• schema-diagram A graphical representation of a
  scheme
• Each part of a scheme is called a schema
  construct

37
Database schema-diagram
38
State (extension)

• A state is a possible and valid filling of data
• Databasestate or snapshot

39
Databasetoestand
40
DBMS architecture

• The three-Schema Architecture
• The internal levalThe desciption of the physical
  level of storage
• Conceptual level conceptueal schema (ER)
• External vies user views

41
(No Transcript)
42
Database languages

• Data-definition language (DDL)
• Storage definition language (SDL)
• View definition language (VDL)
• Data-manipulation level (DML)
• High-level (set-at-a-time)
• Low-level (record-at-a-time)
• Querie language (query language)

43
Database interfaces

• Menu based (browsing)
• Form based (form spec language)
• GUI
• Natural language based
• Special interfaces for parametric users
• Interfaces for the administrator

44
DBMS components

• Stored data manager
• DDL compiler
• Run-time database processor
• Query compiler
• Pre-compiler
• DML compiler

45
(No Transcript)
46
Classification of DBMS

• Based on
• Data models (relational, network, object)
• Number of users (1, some, many)
• Number of terminals (central, distributed)
• Costs
• General / Specific
• Access to the physical level

47
Central architecture

• Centrale architecture
• DBMS runs on a central server (mainframe) from
  terminals the user can access the data
• Some terminals got some dbms function

48
Client / Server architectuur

• Clients are traditionally PC (PCs)
• User-interface
• Cheap and small computers
• Servers are central
• More powerfull
• No user access

49
Client Server Two - Tier

• Server machine runs DBMS (i.e. Oracle, SQLserver)
• Contains all the data and metadata
• Queries are ran from here
• Client machine runs application software and
  communicates with the server
• Via ODBC, JDBC, .NET SQLnet

50
Three-tier

• Server machine runs DBMS Client
• Clients are Web-browsers (thin client)
• Application server is responsible for
  communication with thin client and server

51
Terminal Server

• Thin client runs on pc
• Alle application run on a application server
• Citrix (see UB machines)

52
Databases
DBMS or file
Architecture
Datamodel
Applications
Actors