Database Models and Architecture
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Questions and Answers

Which level of the Three-Schema Architecture describes physical storage?

  • Internal Level (correct)
  • External Level
  • Conceptual Level
  • Representational Level

Logical data independence refers to the ease of changing the storage structure without affecting users.

False (B)

What is a database schema?

A description of database organization that is created during design.

The _____ level of the Three-Schema Architecture shows different parts of the database for different users.

<p>External</p> Signup and view all the answers

Match the following DML types with their descriptions:

<p>High-Level (Set-Oriented) = Works with sets of data Low-Level (Procedural) = Works with one record at a time</p> Signup and view all the answers

Flashcards

Data Model

A way to organize data in a database, including data types, relationships between entities, and rules. Helps retrieve and update data.

Database Schema

A description of how data is organized in a database. Created during design and rarely changes.

Database State

A snapshot of the data in a database at a particular moment in time.

Physical Data Independence

The ability to change the physical storage of data without affecting how users or programs interact with it.

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Data Manipulation Language (DML)

Language used to manipulate data in a database, such as retrieving, adding, deleting, or updating data.

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Study Notes

Data Models

  • Organize data within a database
  • Define data types, relationships, and rules
  • Facilitate data retrieval and updates
  • Categories include:
    • High-level (conceptual): user-friendly
    • Low-level (physical): storage-focused for technical experts
    • Representational: displays structure while hiding storage details

Schemas, Instances, and Database State

  • Database Schema: Describes the database's organization, usually created during design and rarely altered afterward.
  • Schema Diagram: Visually represents the schema, showing structure but not actual data.
  • Database State (Snapshot): Data at a specific moment in time, conforming to schema rules.

Three-Schema Architecture

  • Levels:
    • Internal Level: depicts physical storage
    • Conceptual Level: describes the database structure for all users
    • External (View) Level: presents different parts of the database tailored for different users
  • Goals:
    • Catalog: stores database description
    • Data separation from programs
    • Multiple user view support

Data Independence

  • Logical Data Independence: Changing data structure is difficult without affecting user programs.
  • Physical Data Independence: Changing storage methods is simpler without impacting user programs.

DBMS Language

  • Data Manipulation Language (DML): Used for retrieving, adding, deleting, and updating data.
  • DML Types:
    • High-level (Set-Oriented): operates on sets of data
    • Low-level (Procedural): works on individual records
  • Database Language(SQL):
    • Combines DDL, VDL, DML into a single language
    • DDL: defines schemas
    • SDL: defines internal schemas
    • VDL: defines user views

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Related Documents

Data Models PDF

Description

Dive into the essential concepts of database models, including high-level and low-level structures. Explore the roles of schemas, instances, and the three-schema architecture in data organization and retrieval. Perfect for anyone looking to understand how databases are designed and operated.

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