Chapter 2 Flashcards
What is data model?
Set of describing the data structure, operation and constraints
Main types of data model
Conceptual(close to how user perceive), physical(how data stored), implementation(between booth e.g er) , self describing
What is database schema?
Description of database, structure data type, constraints
What is Database state?
The data stored in that particular moment
What are the Three schema architecture
Internal(describe physical storage structure), conceptual(describes close to how user perceive it) , external( describes the various user views)
The types of data independence:
Logical: can change conceptual without changing external.
Physical: can change the internal without changing conceptual
What is DDL:
Specify conceptual and define internal and external schema
What is DML?
Used to specify data retrievals and updates
Types of DML
High level: specifies what data rather than how
Low level: retrieve data one record at a time
Dbms interface
Stand alone: sql
Programmer: programming language
User friendly:
Mobile: allows transactions
Database system utilities
Loading data from file to database
Backing up database
Monitoring
What is Centralized DBMS architecture?
Combines everything into single system: software,hardware,app etc
Client server vs dbms server:
Client use client software module.
Dbms provide database querie and transaction
Client connect to server via network
Dbms connect via API
2 tier client server architecture
Client installed client module, server install server module
Client program can connect to several dbms
3 tier client server
Common for web app
Intermediate layer called app or web server
Can enhance security
