Download - Lecture Pres 1
-
7/31/2019 Lecture Pres 1
1/21
Database Management
Systems
Peter Blanchfield
-
7/31/2019 Lecture Pres 1
2/21
G6DDBS Blanchfield 2
Before I start
And in case they ever come to my lecture
I owe a lot of this to:
Steve Mills
Michael Hartley
Reproduced with permission (thoughoften in my own words)
-
7/31/2019 Lecture Pres 1
3/21
G6DDBS Blanchfield 3
Assessment
One Exam worth 100%
-
7/31/2019 Lecture Pres 1
4/21
G6DDBS Blanchfield 4
Books
A number of texts in Library
Database Systems, Beynon-Davies pub. Palgrave
Fundamentals of Database Systems, Elmasri & Navathepub. Addison Wesley
Database Systems Date pub. Addison Wesley
Database Systems - A Practical Approach to Design,Implementation, and Management, Connolly & C Begg
pub. Addison-Wesley
-
7/31/2019 Lecture Pres 1
5/21
G6DDBS Blanchfield 5
Overview
Main Topics
Database systems
Models
Design
SQL
Transactions
Concurrency
Administration
-
7/31/2019 Lecture Pres 1
6/21
G6DDBS Blanchfield 6
Overview Continued
Practice
There is no point in learning aboutdatabases if you do not use them
A practical project will be set which willbe assessed during the exam
No course work mark as such will be
awarded
-
7/31/2019 Lecture Pres 1
7/21
G6DDBS Blanchfield 7
Why Study DBMS?
Databases are important
Because they are useful
All sorts of applications
Database Management Systems make
Life easier
Data safer and more secure
-
7/31/2019 Lecture Pres 1
8/21
G6DDBS Blanchfield 8
What is
Data?
In our case information once inelectronically storable and retrievable
form
A database?
A set of such data and of course for us
it is stored in a computer
-
7/31/2019 Lecture Pres 1
9/21
G6DDBS Blanchfield 9
What is
A database system?
Data
Software
Hardware
Users!
-
7/31/2019 Lecture Pres 1
10/21
G6DDBS Blanchfield 10
What is
A Database Management System(DBMS)?
The software that controls the data in a
database
-
7/31/2019 Lecture Pres 1
11/21
G6DDBS Blanchfield 11
Why is this different froma file system?
In the old days
Any new database was organised by thedeveloper
Any new functions were specificallycreated
Thus not reusable
No standards
Data duplication, dependence
Did not aid security, recovery,concurrency etc
-
7/31/2019 Lecture Pres 1
12/21
G6DDBS Blanchfield 12
So a DBMS will
Provide users with a
Data Definition Language (DDL)
Data Manipulation Language (DML)
Data Control Language (DCL)
Which are often all one piece of software Provide for
Persistence
Concurrency
Integrity Security
Data independence
-
7/31/2019 Lecture Pres 1
13/21
G6DDBS Blanchfield 13
DBMS works withMetadata
This is data about the data
Used by the rest of the system
Will thus:Hold descriptions of the database
objects (tables, users, rules, views etc)
Hold information about who is doingwhat
Hold schemas and mappings
-
7/31/2019 Lecture Pres 1
14/21
G6DDBS Blanchfield 14
Relational Systems
E. F. Codd 1970 A relational Model for LargeShared Databanks
Introduced the relational model
Information stored as records in relations (tables) Sound mathematical basis
Model covers data
Structure
Integrity
Manipulation
-
7/31/2019 Lecture Pres 1
15/21
G6DDBS Blanchfield 15
ANSI/SPARC
Standards have been developed
American National Standards Institute
Standards Planning and Requirements
Committee
Three level architecture
System designer internal level
Database designer - conceptual User external level
-
7/31/2019 Lecture Pres 1
16/21
G6DDBS Blanchfield 16
Internal
Physical storage
Structure
Indexes
Used by systems programmers
-
7/31/2019 Lecture Pres 1
17/21
G6DDBS Blanchfield 17
Conceptual
Organisation of the data as a whole
Data abstraction
Used by database administrators andapplication programmers
-
7/31/2019 Lecture Pres 1
18/21
G6DDBS Blanchfield 18
External
Provides the view determined by the user
Data may be hidden
Data may be presented in a suitable form
Used by users and applications programmers
-
7/31/2019 Lecture Pres 1
19/21
G6DDBS Blanchfield 19
Mappings
Translate between layers
Provide data independence
Physical data independence
Changes to internal should not affectconceptual
Logical data independence
Conceptual changes should not affect external
-
7/31/2019 Lecture Pres 1
20/21
G6DDBS Blanchfield 20
Architecture
User 3User 1 User 2
DBA
Stored
Data
ExternalView 1
ExternalView 2
ConceptualView
External Schema
Conceptual Schema
Internal Schema
Mappings
Mapping
-
7/31/2019 Lecture Pres 1
21/21
G6DDBS Blanchfield 21
We did:
What is a database management system?