INTRO TO DATABASE SYSTEMS
DBS: database system, computerized record keeping system
DBMS: Database management system, set of programs forbDB management
End Users: communicate with software systems/apps->comm w/ DBMS->comm w/ operating system to store/extract
OBJECTIVES:
security, reliability, flexibility, ease of access, accuracy, clarity, availability
DATA INDEPENDENCE:
immunity of app programs to changes in structures and access
ADVANTAGES:
reduce redundancy, avoid in constituencies sharable standards integrity
1. External- individual user view
2. Conceptual- abstract rep of info
3. Internal- low level rep of data
Conceptual-internal mapping: conc records repped at internal level
External-conceptual: ext views linked to conpt level
DBMS
definition manipulation security access maintenance
DDS
Data definition subsystem: tools and utilities for defining and changing DB
RELATIONAL MODELS
(see book for charts)
Domain- scalar values attributes drawn
Languages:
SQL OQL XQUERY SQL/XML
Examples found on last link
No comments:
Post a Comment