1.2: Database Systems, An Architectural Overview

Question 1

Three-Level Database Architecture

Answer 1

External Schema
Conceptual Schema
Physical Schema

Question 2

External Schema (External / View Levels)

Answer 2

Views of separate user groups (DB that is relevant for users/user groups.

Question 3

Conceptual Schema (Conceptual / Logical Level)

Answer 3

Information about existing data and relationships in the DB (information about entities)

Question 4

Physical Schema (Physical / Internal Level)

Answer 4

Describes how data are physically stored on disk. (data structures, algorithms)

Question 5

Database Schema

Answer 5

Describes the structure/design of DB

Question 6

Database State

Answer 6

A concrete instance of DB.

Question 7

Data Independence

Answer 7

Property that higher levels of the model are NOT influenced by changes of lower levels.

Question 8

Logical Data Independence

Answer 8

changes in CONCEPTUAL schema do not have impact on External Schema

Question 9

Physical Data Independence

Answer 9

changes of the PHYSICAL schema do NOT impact Conceptual Schema, or External

Question 10

Data Definition Language (DDL)

Answer 10

allows:
manipulate a database schema
(meta) data for the description of a schema. (data dict, sys catalog)
permits specification of implementation details (add certain requirements)

Question 11

Data Manipulation Language (DML)

Answer 11

non-procedual language - user specifies WHICH data are searched for but not HOW data can be found.
allows:
query language - for the retrieval of data objects in a database
“actual” data manipulation language for the change, insertion, deletion of stored data

Question 12

What are the types of database languages

Answer 12

Data Definition Language (DDL)
Data Manipulation Language (DML)