lecture pres 1

7/31/2019 Lecture Pres 1

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Database Management

Systems

Peter Blanchfield


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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)


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Assessment

One Exam worth 100%


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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


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Overview

Main Topics

Database systems

Models

Design

SQL

Transactions

Concurrency

Administration


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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


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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


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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


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What is

A database system?

Data

Software

Hardware

Users!


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What is

A Database Management System(DBMS)?

The software that controls the data in a

database


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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


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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


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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


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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


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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


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Internal

Physical storage

Structure

Indexes

Used by systems programmers


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Conceptual

Organisation of the data as a whole

Data abstraction

Used by database administrators andapplication programmers


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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


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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


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Architecture

User 3User 1 User 2

DBA

Stored

Data

ExternalView 1

ExternalView 2

ConceptualView

External Schema

Conceptual Schema

Internal Schema

Mappings

Mapping


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We did:

What is a database management system?

lecture pres 1

Documents