Relational Databases Overview

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Questions and Answers

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

  • Fifth Normal Form
  • Second Normal Form
  • First Normal Form (correct)
  • Third Normal Form

What is the main purpose of normalization in database design?

  • To ensure all entities are represented in a single table
  • To increase redundancy and improve retrieval speed
  • To organize data in a way that minimizes redundancy and maintains integrity (correct)
  • To eliminate the need for keys in relationships

In an ER diagram, how is an entity represented?

  • A rectangle (correct)
  • A diamond
  • A circle
  • An oval

Which step in ER model creation involves specifying the relationships between identified entities?

<p>Define relationships (C)</p> Signup and view all the answers

What is a characteristic of a foreign key in a database?

<p>Must always point to a primary key (D)</p> Signup and view all the answers

What is the significance of eliminating partial dependencies in the second normal form?

<p>To ensure all non-key attributes depend on the primary key entirely (D)</p> Signup and view all the answers

Which process involves determining how a logical schema will be physically stored in a database management system?

<p>Physical implementation (A)</p> Signup and view all the answers

Which type of relationship allows many employees to enroll in many trainings?

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

What is the primary purpose of a primary key in a relational database?

<p>To identify each row in a table uniquely (B)</p> Signup and view all the answers

Which statement best describes a foreign key in relational databases?

<p>It establishes a link to a unique row in another table (C)</p> Signup and view all the answers

How do relationships contribute to data integrity in relational databases?

<p>By preventing invalid data from being inserted through foreign key constraints (D)</p> Signup and view all the answers

What is a significant benefit of using entity relationship diagrams (ER diagrams) in database design?

<p>They identify and define how entities interact and relate to one another (D)</p> Signup and view all the answers

Which of the following is NOT a benefit associated with establishing relationships in relational databases?

<p>Complexity in data organization (A)</p> Signup and view all the answers

In the context of relational databases, which of the following statements best illustrates how data redundancy is reduced?

<p>By referencing shared information across multiple tables instead of duplicating it (A)</p> Signup and view all the answers

What role do columns play in a table within a relational database?

<p>They define the attributes of the records in the table (B)</p> Signup and view all the answers

How do complex queries benefit from relationships in relational databases?

<p>They enable the retrieval of related data across multiple tables (A)</p> Signup and view all the answers

Flashcards

Relational Database

A type of database that stores and provides access to data points related to each other. Data is organized in tables with rows and columns representing entities and records.

Table

A fundamental structure to store data in a relational database. It has a unique name, rows representing records, and columns defining attributes.

Relationships

Links established between tables in a relational database. Used for complex queries and data integrity.

Primary Key

A column or set of columns in a table that uniquely identifies each row.

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Foreign Key

A column or set of columns in one table that uniquely identifies a row in another table. Establishes a link between the two tables.

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Data Integrity

Ensuring data accuracy and consistency. Foreign key constraints prevent invalid data from being inserted.

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Data retrieval

Retrieving related data from multiple tables in a database. Allows complex queries.

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Data redundancy

Avoiding data duplication across tables by storing related information in separate tables.

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One-to-One Relationship

A relationship where one entity is associated with only one other entity. For example, one person has only one unique ID (DNI).

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One-to-Many Relationship

A relationship where one entity is associated with multiple other entities. For example, one school can have many students.

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Many-to-One Relationship

A relationship where multiple entities are associated with a single entity. For example, many employees can work at the same store.

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Many-to-Many Relationship

A relationship where multiple entities are associated with multiple other entities. Example: Many employees can enroll in several trainings, and many trainings can have multiple employee enrollments. This scenario needs an intermediate table that connects employees and trainings.

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Normalization

A process of organizing data to minimize redundancy and ensure data integrity. It reduces duplications and ensures consistency in data.

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1st Normal Form

The first level of normalization, ensuring that each column contains atomic values. Atomic values are individual components, not a combined entity.

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2nd Normal Form

The second level of normalization, ensuring that all non-key attributes are fully dependent on the primary key. This eliminates situations where a non-key attribute relies on only part of the primary key.

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3rd Normal Form

The third level of normalization, eliminating dependencies between non-key attributes. This ensures that non-key attributes are directly dependent on the primary key, not on other non-key attributes.

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Study Notes

Relational Databases

  • Relational databases store and access related data points.
  • Data is organized in tables with rows (records) and columns (fields).
  • Each table represents a specific entity.
  • Tables are linked through relationships defined by keys.

Tables

  • Fundamental structure in relational databases.
  • Contain rows (records) and columns (attributes).
  • Columns define attributes, rows include data instances.
  • Each table has a unique name.

Relationships

  • Essential for linking tables and ensuring data integrity.
  • Established by keys, enabling complex queries.
  • Primary Keys: Columns uniquely identify rows within a table.
  • Foreign Keys: Columns in one table referencing unique rows in another table, establishing relationships.

Importance of Relationships

  • Data Integrity: Ensures data accuracy and consistency.
  • Foreign key constraints: Prevent invalid data insertion (e.g., preventing an order referencing a non-existent customer).
  • Efficient Data Retrieval: Enables complex queries across multiple tables (e.g., retrieving customer orders).
  • Reduced Data Redundancy: Storing data only once in related tables, minimizing duplication.

Entity Relationship Diagrams (ERDs)

  • Conceptual in Relational Databases
  • Assist in identifying entities, attributes, and relationships between entities.
  • Entity: Represented by rectangular boxes.
  • Attributes: Represented by ovals.
  • Relationship: Represented by diamonds.

Relationship Types

  • One-to-One: One entity to only one other.
  • One-to-Many: One entity to many others.
  • Many-to-Many: Many entities to many others (managed through intermediate tables).

Normalization

  • Organizes data efficiently to prevent redundancy and ensure data integrity.
  • Eliminates redundancy using primary and foreign keys.
  • Reduces transitive dependencies.
  • 1NF (First Normal Form): Each column contains only atomic values (single data items).
  • 2NF (Second Normal Form): Eliminates partial dependencies, where non-key attributes depend only on part of the primary key.
  • 3NF (Third Normal Form): Eliminates transitive dependencies; non-key attributes depend only on the primary key and not on other non-key attributes.

Database Design

  • Defining the structure, storage, and retrieval mechanisms of a database system.
  • Scheme Definition: Defines tables, fields, data types, and relationships.
  • Normalization: Ensures data integrity and reduces redundancy.
  • Physical Implementation: How the logical database schema is physically stored and accessed.
  • Performance Optimization: Includes indexing, partitioning, and query optimization to enhance performance.

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