1. Chapter 1
Introduction

2. Basic Concepts of Database Systems
Database is
A collection of data organized in some way
grouped on what they refer to, or on technical types
relationships between pieces of data determined
Data = symbols for recording and communication (e.g., customer ID and name)
Example: Think of records (paper, electronic) describing employees.
The organization of data can be explained by metadata.
Metadata define how data are organized (e.g., Employee is a class of data, which has x number of attributes, and each attribute belongs to a data type).
EmployeeID Number
LastName Text
FirstName Text
Phone Number
More 

3. Basic Concepts Database Management System (DBMS)
Software for creating databases, storing & retrieving data, creating user interface (forms), creating reports, and administering a DB system (security, access, etc.).
DBMS Product (a specific DBMS software; same as “DBMS Brand”).
Database System (DBMS Application, Application)*:
An implementation of a DBMS product including one or more databases, logic (business rules), some code, and user interface.
Supporting various information needs.
An information system that results from “applying” a DBMS or a database.
Supporting specific information needs.
*But the term “application” is used in various ways, and sometime it means just user interface (forms) or stored queries
and reports. In a more general systems vocabulary, “application” is one of the most used words and abused as
well, as it means different things to different people.

4. File (Processing) Systems vs. DB systems (DBS)
History but also a frequent shortcut today (e.g., Excel as surrogate of DBS)
File Processing Systems:
Data files and program files (code) that work on data files, or
Data and code in the same file
Separate code (functionality) for data input, modification, retrieval, & deletion.
Data files are closely coupled with programs that define metadata - tight coupling reducing design flexibility (changes).
More 

5. File (Processing) Systems vs. DB systems
DBS are:
Higher on retrieval capabilities
Lower redundancy, higher data integrity
Data independent from programs (code); looser coupling –
changes in data and code less restricted
Better security and management of concurrent access to database
Significantly lower development and maintenance cost
But keep in mind: Excel’s enduring popularity in companies.

6. Modifying Data in DBS -- Data-Program independence
Add cell tel. number to employee table
Open table template
Add data element
Existing reports, queries, code will not crash although need to be modified to output new data – looser coupling
Field Name Data Type Description
EmployeeID Number Autonumber..
TaxpayerID Text Federal ID
LastName Text
FirstName Text
. . .
Phone Text Phone Number
CellPhone Text Cell Phone No.

7. DB System Components D B M S Database Database Engine: Form Builder
CRUD* operations & Data Dictionary
Concurrency & Lock Manager
Recovery Manager
Disk Space Manager
Data & Metadata
Management
Security
Management
Query Processor
Retrieval
Form
Builder
Report
Writer
Input/Output;
User Interface
Application
Generator
System development
tools
*CRUD= Create, Read, Update, Delete
Note: The Post book mixes “database” With “data” and “application”.

8. Creating Outputs via Report Writer
Database 4 3
Database Engine 5
Query Processor 2
Report Writer 1 6
Output: Report

9. Relational Database Standard
“Relation” = table, a logical view of the data
structure for storing data.
An example of Table (Sale) created in Oracle.

10. Examples of Relational DBMS Products
Oracle
Sybase
Informix (Unix)
DB2, SQL/DS (IBM)
Access, SQL Server (Microsoft)
Many limited to PC (MS Access, dBASE, Paradox, …)
Open source: MySQL (more)

11. Hierarchical Database
First commercial standard (IBM’s IMS)
Still used in legacy systems
To retrieve how many of item A are sold, start at the top from Customer. Then all nested data are retrieved top-down and left-right.
Different data models needed for different retrieval tasks (e.g., Order at the root) =>
high data redundancy in DBS!
Customer
XYZ
Order 1
Item A
Order 2
Item B
Item C
Entry point
pointers
Customers
files
Item# ItemName Quantity
998 Dog Food 12
764 Cat Food 11
Items
Order
files

12. Network Database Customer XYZ Order 1 Order 2 Entry point Entry points
Item A
Item B
Item C
Relationships between records also
supported by pointers;
complex programming.
One data model supports different retrieval paths (by
customer, order, item).

13. Relational Database Customer(CustomerID, Name, …)
Foreign Key (FK)
Primary Key (PK, Key)
Customer(CustomerID, Name, …)
Order(OrderID, CustomerID, OrderDate, …)
ItemOrdered(OrderID, ItemID, Quantity, …)
Item(ItemID, Description, Price, …)
Data organized as logical tables, consisted of rows (records) and columns (attributes), and connected via key attributes.
Possible to retrieve almost any combination of rows and columns, and a specific piece of data (field) within a row.
Pointers transparent to developers, just need to specify Primary Key (PK)—Foreign Key (FK) relationships.

14. Object-Oriented Databases
Pure OODB: a storage of objects with various retrieval techniques depending on objects’ APIs. Rare in business.
Extends data types and methods over relational DB.
Takes advantages of OO capabilities (e.g., inheritance).
Customer
CustomerID
Name …
Add Customer
Drop Customer
Change Address…
Government
ContactName
ContactPhone
Discount, …
NewContact
Corporate
AddNewContact
Order
OrderID
NewOrder
DeleteOrder
Procedures (behavior,
methods) for processing
data.
Data
Inheritance in Generalization/Speci-
alization relationship

15. Object-Relational DB Systems
More frequent than pure object-oriented systems
Architecture:
Database is relational
Objects are created in main memory according to class diagram and business rules, and populated by data from the relational databases (data access layer in system sequence diagrams). Extended data and method capabilities in objects.
System operations are performed by objects