Data at the Coreof the Enterprise

Objectives Define of database systems Introduce data modeling and SQL Discuss emerging requirements of

database systems

DATA

INFORMATION

?

Attributes of data Sharable Moveable Secure Accurate Timely Relevant

Data hierarchy Bits Characters Fields (columns) Records (rows) Files (table) Database

Why build a database? Handle large amounts of data Satisfy multiple users Make information retrieval faster Make data input faster Provide greater accuracy

Database versus Database Management System (DBMS) Database is a self-describing collection

of integrated files A DBMS is a complex computer

program that acts as a data librarian, supervising the transfer of data between the end user and the database

Advantages of DBMS More info from the same data Reduction of data duplication Improved data integrity Programs are independent of the data

format Sharing of data resources

…and disadvantages Added expense More hardware may be needed If it crashes…. Sophisticated design and programming

required Additional training Security is critical

Relational model Relation? Attribute? Tuple? Keys

Primary and foreign

Referential integrity Relational algebra

Relational DB rules

Every row must have exactly the same number of columns (fields or attributes)

Each row can have only one value stored in each column (fields or attributes)

A column must contain the same kind of value in every row of that column

No two rows can be exactly the same The order of the rows or of the columns can’t

be used to provide information

Terminology

Data Processing

InformalRelational DB

Formal Relational DB

 

File 

Table 

Relation

Record Row Tuple

Field Column Attribute 

 

Data modeling Purpose: control and visualization Process: gathering requirements Results: forms and diagrams

Normalization Purpose:

Avoid anomalies Reduce redundancy

Process: Successive application of rules Bottom-up (data drives process) Move from first through fifth normal form Does it make more or less tables?

Entity relationship modeling List the entities or objects in the

environment People, things, transactions

Describe the relationship between them A single row in table A can be related to

how many rows in table B (one or many) A single row in table B can be related to

how many rows in table A (one or many)

ERD questions What are the subjects/objects of the

business?data entities

What unique characteristic(s) distinguishes each object from others of same type?

primary key

What characteristics describe each object?attributes

How do you use this data?controls & meaning

ERD questions Over what period of time are you interested in

this data? cardinality & time dimensions

Are all instances of each object the same?supertypes, subtypes, aggregations

What events occur that imply associations between objects? relationships (cardinality & degree)

Is each activity or event always handled the same way or are there special circumstances?

integrity rules, cardinality, time

SQL Definition (DDL)

CREATE, ALTER, DROP

Manipulation (DML) SELECT, INSERT, UPDATE, DELETE

What’s the most used sql command?

General format of SELECT

SELECT [DISTINCT] item(s) FROM table(s) [WHERE condition] [GROUP BY columns] [HAVING condition] [ORDER BY row(s)]

Current RDBMS

Emerging data requirementsComplex

Simple

Unstructured Structured

Audio StreamsImages

Video Streams

Text

GraphicsAudio

Spatial Data

Time Series

HTML/SGML

Video

Summary Defined of database systems Introduced data modeling and SQL Discussed emerging requirements of

database systems