1. Supplement 01a Database-Introduction-1
And Franchise Colleges
HSQ - DATABASES & SQL
Supplement 01a Database-Introduction-1
By MANSHA NAWAZ
Supplement 01 (a)
Database-Introduction-1

2. Database-Introduction-1
Why Database Systems?
Data is one of the most important resources in ALL organisations. Without data it is not possible to operate.
Control manufacturing processes?
Process sales of goods?
Diagnose patients’ illnesses?
Forecast sales?
Run the University of Teesside?
To be useful data must be processed into information. It must be:
Accurate
Timely
Relevant
Therefore, you need adequate facilities for storing data and processing information:
Storing (and verifying) data
Manipulating data
Extracting data
Supplement 01 (a)
Database-Introduction-1

3. Supplier, Part#, Part#, Cost, Qty
File - based approach
From the earliest days computers were used to store files of data.
Separate systems, ie separate files and programs, were developed for each application, eg stock files, production files, accounts files, etc.
Applications processed the data to provide information.
Data
Application
Department
Part No, Supplier, qty
location, reorder qty
Stock Control
Stores
Problems
Inconsistency
Redundancy
Lack of integration
Lack of control
Part#, qty, Assy#,
Machine#, Cert.#:
Production
Operations
Supplier, Part#, Part#, Cost, Qty
Accounts
Finance
Supplement 01 (a)
Database-Introduction-1

4. Database approach Stock Control Database Management System Production
DBMS is the environment used to manage a database
The database consisting of stored data and processed information for a system
Data are organised into a single set of underlying TABLES from which the applications draw the data to provide information that are relevant to them.
Application
Department
Stock Control
Database
Database
Management
System
DBMS
Supplier, Supplier Pt No:, Part No:
Cost, Qty ordered, Qty del., qty, Assy No:,
Machine No:, Cert. No: location, reorder qty
Production
Accounts
Supplement 01 (a)
Database-Introduction-1

5. Database Development NF DBMS TABLES FORMS Systems Analysis & Design
DFD DataStores, DataFlows and Data Dictionary
DATA MODEL
TABLE SET NF
E-R Model
DBMS
PHYSICAL VIEW OF DATA
TABLES
LOGICAL VIEW OF DATA
FORMS
Database connectivity via websites
www .net technology
Macromedia Dreamweaver
MS Visual Studio
Database connectivity via desktop DBMS such as
MS Access
Database connectivity via programming languages such as MS Visual Basic
Supplement 01 (a)
Database-Introduction-1
Area of Interest

6. Client/Server Architecture
Server provides services for the Clients which are responsible for interacting with the users (Input/Output)
Server is responsible for performing a service (e.g. transaction) and guaranteeing the integrity of the data
Well suited for distributed systems handling large amounts of data
User Workstation
Operator
Workstation
Department
File-Servers
Corporate
Servers
Supplement 01 (a)
Database-Introduction-1

7. System Development Overview
Systems development undertaken by using Case Tools
used early in development life cycle
Provide requirements and design in terms of Systems Model and Data Model
Case Tools for Systems Modelling:
Dataflow Diagrams (DFD)
Data Dictionary (DD)
Case Tools for Data Modelling:
Normalisation (NF)
A rules based technique undertaken to produce the data model for a system
Entity Relationship Model (ER)
A diagrammatic based technique undertaken to produce the data model for a system
DFD & DD provide us with the base for a ERD Data Model
Data Model
Can be implemented on a DBMS such as MS SQL Server, MS Access, etc
Consists of logical and physical view of the proposed systems data.
DBMS – implementation platform
Database Management System such as MS SQL Server 2000 (MS Access)
Supplement 01 (a)
Database-Introduction-1

8. MS SQL Server V MS Access
MS SQL Server is a server based database.
Multi User – Multi Platform Systems
Large, high volume traffic database systems
Server holds database. Workstation provides access.
For web or database systems if the access traffic is likely to generate more than 20 concurrent database hits at a time, it's time to move to a database server
Generally, database servers like MS SQL Server are the way to go for database or web/database systems
Many and wide ranging user base for system
Additional Security and Login features
MySQL (free sql database used for connectivity to Websites via PHP).
MS Access is Desktop based
Small, low-traffic database systems
Small, low-traffic web sites requiring database connectivity.
Cannot handle heavy traffic from multiple users.
Supplement 01 (a)
Database-Introduction-1

9. Advantages of the Database Approach
No unnecessary duplication of data.
Greater consistency of data.
Wider availability of data.
Greater flexibility of use of data.
Improved data integrity.
Improved security.
Improved backup and recovery services.
Can change the data structure without altering associated programs.
A database is dynamic: it can grow and change.
Data management can be more consistent and systematic.
Supplement 01 (a)
Database-Introduction-1

10. Database-Introduction-1
Databases
“A shared collection of logically related data, and a description of this data, designed to meet the information needs of an organisation.”
‘Database Systems’ by Connolly & Begg Addison-Wesley, ISBN
“A database system can be thought of as a computerised record-keeping system. Such a system involves the data itself (stored in the database), hardware, software and – most important! – users.
… Databases are integrated and (usually) shared; they are used to store persistent data.”
‘An Introduction to Database Systems’ by C J Date, Addison-Wesley, ISBN (7th Edition, 2000)
Supplement 01 (a)
Database-Introduction-1

11. Database-Introduction-1
DBMS
“A software system that enables users to define, create, maintain, and control access to the database.”
Provides the interface between the user and the data in the database.
Allocates storage to data and maintains indices so that any required data can be retrieved.
Protects data against unauthorised access.
Safeguards data against corruption.
Provides recovery and restart facilities after a hardware or software failure.
Supplement 01 (a)
Database-Introduction-1

12. Database-Introduction-1
Data Model
Also referred to as Conceptual Model
A Data Model provides a particular way of thinking about data, at least in terms of its structure
Data Models include data descriptions, data relationships, data semantics, consistency constraints [Silberschatz et. al.]
Data model comprises three components: data structures, data manipulators, and general integrity rules [Codd (1970)]
A Data Model is implementation independent
Not aimed at any particular computer software or hardware.
DBMS supports an implementation of one or more Data Models
What data model is supported by a Relational Database Management System (Access, SQL, Oracle, etc.)
A RDBMS may have extensions to support other models.
At what stage in the Systems Development Lifecycle will data modelling take place (early, middle, late)?
Supplement 01 (a)
Database-Introduction-1

13. Database-Introduction-1
Data Model
Data Models produced early in Systems Development
Makes improvements in terms of :
NO DUPLICATION or REDUNDANT or NULL INFORMATION
REDUCTION IN PHYSICAL SIZE
QUICKER INFORMATION RETRIVAL
LEADS TO A FULLY OPTIMISED SET OF TABLES
Data Model produced by Case Tools techniques
Normalisation
Rule based technique for transfering logical datastore view to physical view
Entity Relationship Modelling.
Diagrammatic representation of a proposed systems database requirements
Data Model provides
a full set of related tables and data
Able to derive physical views (internal schema) of data
Able to derive logical views (external schema) of data
Supplement 01 (a)
Database-Introduction-1

14. Entity Relationship Modelling (ERM)
Normalisation (NF)
Provide us with a Bottom Up approach to producing the database tables
Technique covered in other modules
Supplement on Normalisation is provided on the DD website
Entity Relationship Modelling (ERM)
A data modelling CASE Tool Technique of interest
A diagrammatic representation of a systems database tables
Top Down approach to data modelling
Entity Relationship Diagram (ERD) used to map data model
Applying rules, translate ERD into a set of well-normalised tables
Provides both logical and physical view of tables
Supplement 01 (a)
Database-Introduction-1

15. Database-Introduction-1
PHYSICAL VIEW
TABLES
DATA
Internal Schema View
database structure view that a DBMS requires.
in terms of Tables, Attributes (data fields) and Types (data defn.)
linkage between tables via primary and foreign keys
All Datastores decomposed to a set of TABLES
Physical View – for Designers
LOGICAL VIEW
FORMS
INFORMATION
External Schema View
Form or Screen views provided to the end user.
A set of FORMS derived from the TABLES
Logical View – for Users
Supplement 01 (a)
Database-Introduction-1

16. The Three Level ANSI-SPARC Architecture
In 1975 the ANSI Standards Planning and Requirements Committee proposed a standard terminology and general architecture for database systems.
The objective is to separate each user’s view of the database from the way it is physically represented. 3 levels or views of data within a database:
External Level
The users’ view of the database. Also known as the applications view.
Conceptual Level
The overall view of the database. Also known as the global view.
Internal Level
The physical representation of the database on the computer. Also known as the storage view.
Supplement 01 (a)
Database-Introduction-1

17. Database-Introduction-1
Schemas
The overall description of the database is called the database schema. There are 3 different types of schema in the database.
External Schema
There are multiple external schemas (or subschemas), each one corresponding to a different view of the data.
Conceptual Schema
There is one conceptual schema, which describes the data stored in the database, the relationships and the integrity constraints.
Internal Schema
There is one internal schema, which describes how the data are stored in the database and how they are accessed.
Supplement 01 (a)
Database-Introduction-1

18. Database-Introduction-1
Schemas and Views
Conceptual
Inventory
H R
Finance
Production
Customer
Service
External
External
Internal
Supplement 01 (a)
Database-Introduction-1

19. Database-Introduction-1
Mapping
Provides the translation between the schemas at different levels. The DBMS is responsible for mapping between the 3 types of schema.
The DBMS must ensure that each external schema is derivable from the conceptual schema.
The DBMS must use the information in the conceptual schema to map between each external schema and the internal schema.
Supplement 01 (a)
Database-Introduction-1

20. Database-Introduction-1
Data Independence
A major objective for the 3-level architecture is to provide data independence, ie upper levels must be unaffected by changes to lower levels.
There are 2 kinds of data independence:
Logical data independence
refers to the immunity of the external schemas to changes in the conceptual schema.
It should be possible to alter tables, columns or relationships without having to alter existing external schemas or rewrite application programs (other than those that are directly affected).
Physical data independence
refers to the immunity of the conceptual schema to changes in the internal schema.
It should be possible to alter file organizations, storage devices, indexes, etc, without having to alter the conceptual or external schemas.
Supplement 01 (a)
Database-Introduction-1

21. Database-Introduction-1
The Systems Catalogue
The database schema is defined using a special language called a Data Definition Language (DDL).
The result of the compilation of the DDL statements is a set of tables stored in special files collectively called the system catalog.
This is a repository of meta-data (data about data), ie information describing the data in the database, typically containing the name, description, source and usage information for each data item.
The system catalog is also known as the data dictionary or the data directory.
Supplement 01 (a)
Database-Introduction-1

22. Database-Introduction-1
Database Language
A Data Definition Language (DDL) is used to specify the data in the database.
A Data Manipulation Language (DML) is used to access the data.
A Data Control Language (DCL) is used to control access to the data.
Some databases have a combined DDL, DML and DCL (often called a Query Language), eg SQL.
Supplement 01 (a)
Database-Introduction-1

23. Database Types - 3 Main Data Models
Each database uses a definition language
imposes restrictions on
what can be defined
how entities relate to each other
Hierarchical model
Network model
Relational model
Supplement 01 (a)
Database-Introduction-1

24. Database Types - Network
Can show all 1:n relationships between records
Supplier Name
Supplier Part No:
Link File
Part No:
Supplement 01 (a)
Database-Introduction-1

25. Database Types - Hierarchical
STOCK
Electrical
Steel
Oils
Fasteners
Part No:
Quantity
Supplier Name
Location
Supplier Part No:
Supplier Code
Supplement 01 (a)
Database-Introduction-1

26. Database Types - Relational
Data Files
STOCK ITEM
STOCK ITEM
FILE
Part No:
Colour
Weight
Description
Quantity
Reorder Qty
Location
Supplier Name
Supplier Code
Supplier Part No:
12345
N/A 98
F37
Cadmium Bar 90mm dia 7 4
Ferris F2
c801
RECORD
FIELD(S)
FIELD VALUES
KEY FIELD
PRIMARYKEY
Supplement 01 (a)
Database-Introduction-1

27. Database Types - Relational
Logical vs. Physical
STOCK ITEM
LOGICAL
12345
N/A 98
F37
Cadmium Bar 90mm dia 7 4
Ferris F2
c801
FIELD VALUES
FIELD(S)
Part No:
Colour
Weight
Description
Quantity
Reorder Qty
Location
Supplier Name
Supplier Code
Supplier Part No:
PHYSICAL
Supplement 01 (a)
Database-Introduction-1

28. Database-Introduction-1
Relationships - 1:1
STOCK ITEM
Part No:
12345
N/A 98
F37
Cadmium Bar 90mm dia 7 4
Ferris F2
c801
Quantity
Colour
Reorder Qty
Weight
Supplier Name
Location
Supplier Code
Description
Supplier Part No:
Supplement 01 (a)
Database-Introduction-1

29. Database-Introduction-1
Relationships - 1:n
STOCK ITEM
STOCK ITEM
STOCK ITEM
Part No:
12345
N/A 98
F37
Cadmium Bar 90mm dia 7 4
Ferris F2
c801
12345
Quantity
Colour
Reorder Qty
Weight
Supplier Name
Location
Supplier Code
Description
Supplier Part No:
Supplement 01 (a)
Database-Introduction-1

30. Database-Introduction-1
Relationships - m:n
STOCK ITEM
STOCK ITEM
STOCK ITEM
Part No:
12345
N/A 98
F37
Cadmium Bar 90mm dia 7 4
Ferris F2
c801
12345
Quantity
Colour
Reorder Qty
Weight
Supplier Name
Location
Supplier Code
Description
Supplier Part No:
Supplement 01 (a)
Database-Introduction-1

31. Database-Introduction-1
Relational Model Technique Future Lectures will cover the Entity Relationship Diagrams (ERD’s)
Supplement 01 (a)
Database-Introduction-1