ch 06 database
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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