Relational Databases Overview

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Questions and Answers

Which of the following describes the relationship defined as 'one school has many students'?

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

What is the purpose of normalization in database design?

  • To eliminate redundancy and ensure data integrity (correct)
  • To define relationship constraints within a database
  • To aggregate data from multiple tables into one
  • To automatically generate ER diagrams

Which of the following is considered a primary normal form requirement?

  • Partial dependencies must be maintained
  • Eliminate transitive dependencies
  • Each column must contain only atomic values (correct)
  • All non-key attributes can depend on other non-key attributes

In an ER diagram, what shape represents an entity?

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

What is the effect of having a many-to-many relationship between employees and training?

<p>An intermediate table is required to manage this relationship (C)</p> Signup and view all the answers

Which step is NOT part of the ER model creation process?

<p>Determine data types (D)</p> Signup and view all the answers

What does the term 'foreign key' refer to in a database?

<p>An attribute that creates a link between two tables (B)</p> Signup and view all the answers

Which of the following contributes to performance optimization in database management?

<p>Indexing and query optimization (B)</p> Signup and view all the answers

What role do primary keys serve in a relational database?

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

How do foreign keys contribute to data integrity in relational databases?

<p>They enforce referential constraints to prevent invalid entries. (B)</p> Signup and view all the answers

What is one major advantage of reduced data redundancy in relational databases?

<p>It simplifies complex queries across multiple tables. (B)</p> Signup and view all the answers

What is the primary function of entity relationship diagrams (ER diagrams) in relational databases?

<p>To identify the relationships between different entities. (A)</p> Signup and view all the answers

Which of the following statements correctly describes a relationship in a relational database?

<p>A relationship links data instances of one entity to another entity. (A)</p> Signup and view all the answers

In what way do relational databases ensure efficient data retrieval?

<p>By facilitating joins to access related data across multiple tables. (D)</p> Signup and view all the answers

What is a characteristic of a relational database table?

<p>It consists of rows and columns that represent entities and attributes. (A)</p> Signup and view all the answers

Which statement about relationships in a relational database is most accurate?

<p>They are crucial for maintaining data accuracy and facilitating queries. (A)</p> Signup and view all the answers

Flashcards

Relational Database

A database that organizes data into related tables. Each table has rows (records) and columns (fields) representing entities and their attributes.

Table

The fundamental structure of a relational database, storing data in rows and columns.

Primary Key

A unique identifier for each row within a table. It ensures data integrity and prevents duplicate entries.

Foreign Key

A column or set of columns in one table that links to the primary key of another table, establishing a relationship between them.

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Relationships

Links between tables that ensure data consistency and accuracy. They are established through primary and foreign keys.

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Entity Relationship Diagram (ERD)

A diagram that visually represents entities, their attributes, and relationships between them. It helps understand data structure and relationships between entities.

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One-to-Many Relationship

A type of relationship where one entity can be associated with multiple instances of another entity. E.g., one customer can place multiple orders.

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One-to-One Relationship

A type of relationship where one entity can be associated with only one instance of another entity. E.g., one order can be placed by only one customer.

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Many-to-One Relationship

A relationship where many entities can be associated with one other entity.

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Many-to-Many Relationship

A relationship where many entities can be associated with many other entities. An intermediary table is used to handle this complex relationship.

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Normalization

The process of organizing the data structure in a database to minimize redundancy and maximize accuracy.

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1st Normal Form (1NF)

Ensures that each column (attribute) in a table holds only one piece of data, or atomic value.

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2nd Normal Form (2NF)

Eliminates partial dependencies. Each non-key attribute should rely on the entire primary key, not just a part of it.

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3rd Normal Form (3NF)

Eliminates dependencies on non-key attributes. Each non-key column should directly depend on the primary key, not on other non-key columns.

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Study Notes

Relational Databases

  • Relational databases store and access related data points.
  • Data is organized into tables composed of rows (records) and columns (fields).
  • Each table represents a specific entity.
  • Tables have a unique name, rows contain data instances, and columns define attributes.
  • Relationships are crucial for linking tables and ensuring data integrity.

Relationships

  • Primary Keys: uniquely identify each row within a table.
  • Foreign Keys: uniquely identify a row in another table, creating a link between tables.
  • Relationships ensure data accuracy and consistency.
  • Foreign keys prevent invalid data insertion (e.g., preventing an order from linking to a non-existent customer).

Importance of Relationships

  • Data Integrity: maintains data accuracy and consistency.
  • Efficient Data Retrieval: enables complex queries to retrieve related data across multiple tables.
  • Reduced Data Redundancy: avoids duplicating data by storing related data only once in separate tables.

Entity-Relationship Diagrams (ERDs)

  • ER diagrams visually represent entities, attributes, and relationships.
  • They aid in identifying entities, attributes, and relationships between entities within a database.

Database Design Steps

  • Identify entities
  • Define relationships
  • Determine attributes
  • Specify keys like primary keys and foreign keys
  • Create the diagram using standard symbols.

Normalization

  • Organizes data efficiently to avoid redundancy.
  • Uses primary and foreign keys.
  • Reduces transitive dependencies.

Normal Forms

  • 1st Normal Form: ensures each column contains only atomic values (individual data points).
  • 2nd Normal Form: eliminates partial dependencies ensuring all non-key attributes depend on the entire primary key.
  • 3rd Normal Form: eliminates non-key attributes that depend on other non-key attributes.

Database Design Overview

  • Database design is the process of creating the structure, storage, and retrieval mechanisms for data.
  • It defines how data is stored, accessed, and managed.
  • Defines tables, fields, data types, and relationships.
  • Ensures minimized redundancy and optimized data integrity.
  • Physical implementation determines how the logical schema is stored and accessed.
  • Performance optimization involves enhancing database performance with techniques such as indexing, partitioning, and query optimization.

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