1: Database Fundamentals and Models Flashcards

(10 cards)

1
Q

What is a Database?

A

A database is a collection of related data, representing an abstracted aspect of the real world and designed for a specific purpose

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2
Q

What is a DBMS

A

A Database Management System is software used to define, construct, manipulate and share databases

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3
Q

What is a database schema?

A

The database schema is the complete definition of the database structure and constraints. It’s stored in the DBMS catalog as metadata

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4
Q

What is a data model?

A

A data model is a collection of concepts to describe database structure, including data types, relationships, and constraints

They provided abstraction levels: High-level (conceptual, e.g., ER), Intermediate (logical/representational/implementation, e.g., Relational), and Low-level (physical)

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5
Q

What is the Three-Schema Framework?

A

This framework decouples user applications from the physical database.

It consists of:
◦ External (View) Level: Describes subsets of the database for specific user/application groups.
◦ Conceptual (Logical) Level: Describes entities, data types, relationships, operations, and constraints, hiding physical storage details.
◦ Physical (Internal) Level: Describes the physical storage structure using a physical data model.

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6
Q

What is the Data Indepndence?

A

The ability to change the schema at one level without forcing changes at the next higher level

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7
Q

What is Logical data independence?

A

Logical data independence allows changes to the logical schema (e.g., adding columns) without affecting external schemas (to a point)

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8
Q

What is Physical data independence?

A

Physical data independence allows changes to the physical schema (e.g., adding indexes) without affecting the logical schema. It separates ‘what’ is retrieved from ‘how’ it is stored

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9
Q

ERDs vs Relational Model

A

ER modeling is a popular way to model requirements at the conceptual/logical level.

The Relational Model is a formal, logical data model with a mathematical basis (set theory, logic).

ERDs are often mapped to relational schemas.

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10
Q

How to do: ERD to relational mapping?

A

Entities become relations. Attributes become columns. Relationships are mapped, often involving foreign keys. Weak entities and identifying relationships require the parent’s primary key as part of the weak entity’s key. M:N relationships are typically resolved into an associative entity (a new relation)

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