Relational Databases Overview
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Questions and Answers

What is the primary objective of normalization in database design?

  • To enable faster data entry processes
  • To create multiple copies of data for redundancy
  • To reduce data redundancy and improve data integrity (correct)
  • To enhance the visual appearance of data

Which of the following relationships is characterized by many employees enrolled in many trainings?

  • One to Many
  • Many to One
  • Many to Many (correct)
  • One to One

In the steps for ER model creation, which step comes last?

  • Draw the diagram using standard ER diagram symbols (correct)
  • Determine attributes
  • Choose keys
  • Define relationships

What does the term 'physical implementation' refer to in database design?

<p>How the logical schema is physically stored and accessed (A)</p> Signup and view all the answers

Which form of normalization requires that each column contains only atomic values?

<p>1st Normal Form (D)</p> Signup and view all the answers

Which type of key is represented by an underlined attribute in an ER diagram?

<p>Primary Key (B)</p> Signup and view all the answers

What is a common technique used for performance optimization in database systems?

<p>Indexing (D)</p> Signup and view all the answers

Which normalization step aims to eliminate non-key attributes that depend on another non-key attribute?

<p>3rd Normal Form (D)</p> Signup and view all the answers

What role do primary keys play in a relational database?

<p>They ensure that every row in a table is uniquely identifiable. (B)</p> Signup and view all the answers

How does a foreign key contribute to data integrity in relational databases?

<p>By ensuring valid references between related tables. (A)</p> Signup and view all the answers

What is a crucial advantage of structuring data in relational databases?

<p>It enhances the ability to execute complex queries efficiently. (A)</p> Signup and view all the answers

Which of the following best describes entity relationship diagrams (ER diagrams)?

<p>They provide a visual representation of entities and their relationships. (D)</p> Signup and view all the answers

What is the purpose of reducing data redundancy in a relational database?

<p>To ensure that data is only stored once and referenced properly. (C)</p> Signup and view all the answers

In relational databases, what does a table primarily represent?

<p>A specific entity with uniquely identified rows. (C)</p> Signup and view all the answers

What does a relationship in a relational database allow for regarding data fetching?

<p>It enables complex queries across multiple related tables. (A)</p> Signup and view all the answers

Why is it important to establish relationships between tables in a relational database?

<p>They help maintain data integrity and enable efficient data access. (B)</p> Signup and view all the answers

Flashcards

Relational Database

A type of database that stores and manages data organized in tables with rows and columns. Each table represents a specific entity, and relationships link these tables to ensure data integrity and allow efficient retrieval.

Table

A fundamental structure in a relational database that stores data. Each table has a unique name and consists of rows (records) and columns (fields). Columns define attributes, and rows contain data instances.

Primary Key

A column or set of columns in a table that uniquely identifies each row. Ensures each row has a distinct label.

Foreign Key

A column or set of columns in one table that references the primary key in another table. Establishes relationships between tables.

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Relationship (in Relational DB)

A connection between tables that allows data from multiple tables to be combined and queried. Enables complex data retrieval.

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Entity Relationship Diagram

A diagram that visually represents the entities in a database and the relationships between them. Helpful for mapping data structure.

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Entity Identification

Identifying the entities involved in a database, the attributes of these entities, and the relationships between them. Key step in designing a database.

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Relationship Definition

Defining how entities interact with each other. It describes the type and extent of relationships between entities.

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One-to-One Relationship

A relationship where one entity is linked to only one other entity. For example, one person has one DNI.

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One-to-Many Relationship

A relationship where one entity can be linked to multiple other entities. For example, one school has many students.

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Many-to-One Relationship

A relationship where multiple entities can be linked to one entity. For example, many employees work in one store.

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Many-to-Many Relationship

A relationship where multiple entities of one type are linked to multiple entities of another type. For example, many employees can enroll in many trainings, and many trainings can have many employees enrolled. This relationship requires an 'intermediate table' to manage the connections.

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Normalization

A process that organizes data to reduce redundancy and improve data integrity. It involves creating tables, defining relationships, and using primary and foreign keys.

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1NF (First Normal Form)

The first normal form (1NF) in database normalization ensures that each column contains only atomic values. This means each word or number should be in a single column.

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2NF (Second Normal Form)

The second normal form (2NF) eliminates partial dependencies. All non-key attributes should depend fully on the primary key.

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3NF (Third Normal Form)

The third normal form (3NF) eliminates non-key attributes that depend on other non-key attributes. This ensures that each attribute is directly related to the primary key.

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Study Notes

Relational Databases

  • Relational databases store and access related data points.
  • Data is organized in tables composed of rows (records) and columns (fields).
  • Tables represent specific entities.
  • Columns define attributes, and rows contain data.
  • Relationships are crucial for linking tables.
  • Relationships ensure data integrity.

Relationships Matter

  • Data integrity: Maintains data accuracy and consistency.
  • Foreign keys: Prevent invalid data by linking between tables properly (e.g., prevent referencing a non-existent customer).
  • Data retrieval: Allows more complex queries across multiple tables.
  • Data redundancy reduction: Eliminates data duplication by storing related data in separate tables (e.g. customers in one table, using reference to that table in orders).

Entity Relationship Diagrams

  • Entity identification: ER diagrams aid in identifying entities, attributes, and relationships between entities.

Relationships Definition

  • Define how different entities interact.
  • Indicate the number of instances of one entity that relate to another entity (one-to-one, one-to-many, many-to-one, many-to-many).
    • Example: One school can have many students (one-to-many).

Normalization

  • Organizes data, avoids redundancy, and increases data accuracy and integrity.
  • Key techniques:
    • Eliminates data redundancy
    • Uses primary and foreign keys
    • Reduces transitive dependencies

Normal Forms (Normalization)

  • 1NF: Each column contains only atomic values (single value per cell)
  • 2NF: Eliminates partial dependencies. All non-key attributes should depend on the whole primary key.
  • 3NF: Eliminates non-key attributes that depend on other non-key attributes.

Database Design

  • Defines database structure, storage, and retrieval mechanisms.
  • Core elements: Schema definition, normalization, physical implementation, performance optimization.
  • Schema definition: Defines tables, attributes, data types, and relationships within a database.
  • Normalization: Minimizes data redundancy and ensures data integrity.
  • Physical implementation: Determines how logical schema is stored and accessed.
  • Performance optimization: Using indexes, partitioning, and query optimization to improve performance.

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Relational Databases PDF

Description

This quiz covers the fundamentals of relational databases, focusing on how data is organized in tables, the significance of relationships between tables, and the importance of data integrity. Additionally, it highlights the role of entity-relationship diagrams in identifying entities and their attributes.

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