CIS Database Notes

Topics: Database, Entity-relationship model, Relational model Pages: 51 (7764 words) Published: September 30, 2014
Introduction to Databases
BDS: Connolly, Begg, Holowczak
Pratt/Adamski
Elmasri/Navathe (3rded.)
Kroenke Book (7thed.)
McFadden (5thed.)
Mata-Toledo / Cushman
Ch. 1 and 2
Ch. 1
Ch. 1 and 2
Chap. 1 and 2
Chap. 1
Schaum's Outlines Ch. 1
Q: What is a Database ?
Answer from BDS: A shared collection of logically related data and descriptions of that data, designed to meet the needs of na organization. Answer from Elmasri/Navathe:
A Database (DB) is collection of related data - with the following properties: 1. A DB is logically coherent and has some relevant meaning
2. A DB is designed, built and populated with data for a specific purpose 3. A DB represents some aspect of the real world.
We can also say that the database is a model of what the users perceive. Three main categories of models:
User or Conceptual Models: How users perceive the world and/or the business. Logical Models: Represent the logic of how a a business operates. For example, the relationship between different entities and the flow of data through the organization. Based on the User's model. Physical Models: Represent how the database is actually implemented on a computer system. This is based on the logical model.  Database Management System (DBMS)

A Software system that enables users to define, create and maintain the database and provides controlled access to the database.  Database System (DBS) contains:
The Database +
The DBMS + 
Application Programs (what users interact with)
 

Note: We will explore how the application, DBMS and database are distributed in the Database System Architecutres module later in the semester. File Systems
File System: A collection of individual files accessed by applications programs Limitations of a File System:
Separated and Isolated Data - Makes coordinating, assimilating and representing data difficult Data Duplication - Wastes space and can lead to data integrity (inconsistency) problems Application Program Dependencies - Changes to a single file can require changes to numerous application programs Incompatible Files

Lack of Data Sharing - Difficult to control access to files, especially to individual portions of files Advantages of a DBMS 
A DBMS can provide:
Data Consistency and Integrity - by controlling access and minimizing data duplication Application program independence - by storing data in a uniform fashion Data Sharing - by controlling access to data items, many users can access data concurrently Backup and Recovery

Security and Privacy
Multiple views of data
Example Database
An Example Database
CustomerID
Name
Address
City
State
Acct_Number
Balance
123
Mr. Smith
123 Lexington
Smithville
KY
9987
4000
123
Mr. Smith
123 Lexington
Smithville
KY
9980
2000
124
Mrs. Jones
12 Davis Ave.
Smithville
KY
8811
1000
125
Mr. Axe
443 Grinder Ln.
Broadville
GA
4422
6000
125
Mr. Axe
443 Grinder Ln.
Broadville
GA
4433
9000
127
Mr. & Mrs. Builder
661 Parker Rd.
Streetville
GA
3322
500
127
Mr. & Mrs. Builder
661 Parker Rd.
Streetville
GA
1122
800
What happens when a customer moves to a new house ?
Who should have access to what data in this database ?
What happens if Mr. and Mrs. Builder both try and withdraw $500 from account 3322 ? What happens if the system crashes just as Mr. Axe is depositing his latest paycheck ? What data is the customer concerned with ?

What data is a bank manager concerned with ?
Send a mailing to all customers with checking accounts having greater than $2000 balance Let all GA customers know of a new branch location
Brief History of Database Systems
1940's, 50's Initial use of computers as calculators. Limited data, focus on algorithms. Science, military applications. 1960's Business uses. Organizational data, customer data, sales, inventory, accounting, etc. File system based, high emphasis on applications programs to extract and assimilate data. Larger amounts of data, relatively simple calculations....
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