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Questions and Answers
Which level of the Three-Schema Architecture describes physical storage?
Which level of the Three-Schema Architecture describes physical storage?
Logical data independence refers to the ease of changing the storage structure without affecting users.
Logical data independence refers to the ease of changing the storage structure without affecting users.
False
What is a database schema?
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.
The _____ level of the Three-Schema Architecture shows different parts of the database for different users.
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Match the following DML types with their descriptions:
Match the following DML types with their descriptions:
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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
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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
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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.
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DML Types:
- High-level (Set-Oriented): operates on sets of data
- Low-level (Procedural): works on individual records
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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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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.
