1. Information system analysis and design
Dr. Dina Tbaishat

2. Recap
Last lecture we started with the second phase in a system development life cycle – design
According to Kendall and Kendall (2002) , we mentioned that Design can be for: effective input, effective output, databases, user interface, and data entry procedures
Last week we covered the input, output and data entry design, today we shall look at database design

3. introduction Data storage is basic in information systems
To design a good data storage in an information system some objectives should be met, these are:
Assuring purposeful information retrieval
Efficient data storage
Availability of data
Efficient updating and retrieval
Data integrity

4. Basic concepts
Entity: “an object or event about which someone chooses to collect data” (Kendall and Kendall, 2002). Entities are drawn using rectangles
Relationships: associations between entities
Entity Relation Diagram (ERD): a diagram that shows the tables (relations) and their relationships
Cardinality of a relationship: refers to the nature of the relationship between tables, it is the number of instances of entity B that can be associated with entity A

6. Other notations for the cardinality: 1 to many*

7. Attributes: characteristics of entities, things that describe entities
Records: data items that have something in common with the entity described. These are for one instance of the entity
This table is for the entity (student):
Address ID
Last name
First name
Amman
Mazen
Layla
Zarqa
Khalaf
Hoda
Salem
Ali
Smith
John

8. Relational databases are preferred over flat databases since they have no empty records and do not have repeated records
Typical data types are
text (that is, alphabetic characters)
number
date/time
Why is it important to assign a data type for fields ??

9. The data type indicates the operations that can be performed on the field, for example, having numerical data allows arithmetical operations to be performed on the data
Similarly, using the data type ‘date’ allows data to be sorted chronologically
Defining a data type for fields can help prevent the wrong type of data being entered. If a field is defined as containing text data (for instance), the program can perform checks on any data entered to make sure it is the right kind

10. Using keys…
Linking the records in separate tables requires the use of keys
A key uniquely identifies each record of a table. The simplest way to create a key is to create a column with serial numbers so each entity has a unique value for that field
A table may have more than one key for example student number and student's nationality number but one key is chosen to be a primary key

11. Foreign key: is a field (or collection of fields) in one table that uniquely identifies a row of another table, for example, adding “course-key” to the “student table”

12. SQL
When you search a large website for information, for instance when you search a large e- government site, very often, behind the scenes, a large relational database is being searched
SQL is used for extracting information from a database
SQL stands for Structured Query Language
For example, suppose we wanted to find the family names of all students whose average is 2:
SELECT family-name
FROM student
WHERE GPA=2

13. Viewing data
Generally data is viewed in a ‘form’, which is a specially designed interface between the user and the database
There are usually rectangular boxes to show the fields’ values for certain record (patient or student)
The user can scroll forwards and backwards though the records, or search on any field for a particular piece of data
Fields are usually labeled for ease of identification, for example, student name:
These labels are design features of the form; they need not be the same as the entity names or attribute names

14. Good DB design
Break your data into logical pieces (but not too much – name and phone number)
Always have a primary key
Apply normalization, by having no repetitive data. If a table has more than 20 fields, re- think!
Do not use short column names, make it meaningful
Pay attention to data types
Pay attention to constraints!
Always test it

15. exercise
Create ERD for registration process at your university, think of the appropriate tables (entities), their attributes and the possible relationships

16. References
Kendall, K. E., & Kendall, J. E. (2002). Systems analysis and design. USA: Pearson Education