1. Elements of Database System
LECTURE 3
BBA 8TH (M)
Elements of Database System
Database Design Technique
process of database design consist of three major phases
an information requirement analysis phase
a logical design phase
physical design phase

2. Elements of Database Systems
An information requirement analysis phase involves: 1st & most Imp phase
Working with users to define their information needs in detail
Information as users see it
Information is viewed in terms of the way it appears in documents.
On terminal screens
Even images in users mind

3. Elements of Database System
Logical design
Various views have been defined and specification developed, they must be coordinated and organized into an integrated cohesive system.
Process referred to as logical design
Developing a data model for each user view
Integrating the entities, attributes, and relationship into a composite logical schema that describes the database for that module in terms unrelated to the sw package being used

4. Elements of database
3. Transforming the logical schema into a software schema expressed in the language of the chosen database management package.

5. Elements of database A Primary Key Concatenated keys
Uniquely identifies each data item in a group of related items. A primary key is a data item with only single headed arrow.
Concatenated keys
Are formed by joining two or more data items to produce a primary key
A one to many relationship exists between one of the other elements of the group and the key

6. Un-normalized bubble chart
Instructor
High degree
university
year
Course
Text book
fee
date
Organization
Prospect
Title
street
City
zip

7. Un-normalized bubble chart
The last figure is said to be un-normalized; becz it has many-to-many relationships between data items in the same group and one-to-many relationship between non-key items in the same group.
We need to normalize it; means keys have only single headed arrows to items within their data group, although they can have one-to-many relationships with keys of other data groups.

8. Normalized bubble chart
Instructor
High degree
university
year
Course + Date
Standard fee
Text book
Prospect
Title
zip
Organization
street
City

9. Rules to normalize the bubble chart
If a bubble has single headed arrows entering it from other items in its group and leaving it to other items in its group, it is a potential primary key and should be moved into a new group with the items it identifies.
If an items or a group of items has no key, a concatenated key should be formed to serve as an identifier. Names (of people, courses, products), identification numbers (social security number, account number), and dates are likely candidates for concatenated keys)

10. Rules to normalize
The concatenated key should be formed from the fewest number of data items possible to identify the data items in its group

11. Thanks very much!!
Any Questions????????