Database Design and Relational Model
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Questions and Answers

What is the role of a foreign key in a database relationship?

  • To create a unique identifier for each record.
  • To store only numeric data.
  • To establish a relationship between two tables. (correct)
  • To automatically update data in related tables.

In a many-to-many relationship, which entity is typically introduced?

  • A primary entity.
  • A redundant entity.
  • A composite entity. (correct)
  • A tertiary entity.

Which of the following best describes a one-to-many relationship?

  • Each record in one table must link to multiple records in another table.
  • Each record in both tables can link to many records in both tables.
  • One record in a table corresponds to one record in another table.
  • Multiple records in one table correspond to one record in another table. (correct)

What is the function of the composite key in a child entity of a many-to-many relationship?

<p>To uniquely identify records in the child entity. (B)</p> Signup and view all the answers

In the given scenario of employee tracking, what is an example of generalization?

<p>Combining the employee information into a single employee table. (D)</p> Signup and view all the answers

How does specialization differ from generalization?

<p>Specialization creates sub-entities with unique attributes, while generalization combines shared attributes. (A)</p> Signup and view all the answers

In the context of binary relationships, what does the term 'aggregates' refer to?

<p>Collection of attributes that represent a relationship. (B)</p> Signup and view all the answers

What is indicated by the foreign key player_id in the Match_played entity?

<p>It allows multiple matches for a single player. (A)</p> Signup and view all the answers

In the context of a unary relationship, how is a supervisor represented in the employee table?

<p>With a supervisor_id column referencing the employee's id (D)</p> Signup and view all the answers

What is a characteristic of a one-to-one binary relationship?

<p>The primary key of the stronger entity is used as a foreign key in the weaker entity (C)</p> Signup and view all the answers

In a one-to-many relationship, which side typically includes the foreign key?

<p>The side designated as 'many' (B)</p> Signup and view all the answers

What does a many-to-many relationship typically require for implementation in a relational database?

<p>A specialized table that associates the two entities (C)</p> Signup and view all the answers

In the relational transformation process, which relationship type is characterized by an employee supervising other employees?

<p>Unary Relationship (C)</p> Signup and view all the answers

How is specialization reflected in relational databases?

<p>By defining superclasses and subclasses with their attributes (C)</p> Signup and view all the answers

What best describes a foreign key in a one-to-many relationship?

<p>It creates a linkage from the 'many' side to the 'one' side (A)</p> Signup and view all the answers

Which of the following scenarios is an example of a one-to-many relationship?

<p>A manager oversees multiple employees (B)</p> Signup and view all the answers

In the context of the employee relations, what does the Foreign Key ID_Num in the Manager entity reference?

<p>The Employee entity (A)</p> Signup and view all the answers

What characteristic is evident in the specialization and generalization relationship depicted between Manager and Executive?

<p>Employees must exclusively be either a manager or an executive (A)</p> Signup and view all the answers

What type of relationship is established between Player and Player_Email in the context of multi-valued attributes?

<p>One-to-many relationship (D)</p> Signup and view all the answers

Which of the following statements correctly describes the implementation of multi-valued attributes in the context of Player?

<p>The Player_Email table allows shared emails among multiple players (A)</p> Signup and view all the answers

What is the implication of the overlapping specialization regarding employee roles?

<p>Employees may belong to multiple categories simultaneously (D)</p> Signup and view all the answers

Which of the following entities is not listed as part of the overlapping relationship in the employee structure?

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

What does the term 'disjoint specialization' imply in the context of the employee structure?

<p>Employees must belong to one role only, either manager or executive (B)</p> Signup and view all the answers

What is a primary requirement for the ID_num field in the Manager and Executive entities?

<p>It must reference an entry in the Employee entity (D)</p> Signup and view all the answers

Flashcards

Many-to-Many Relationship

A relationship where one record in a table can be related to many records in another table, and vice versa.

Third Entity

A new table created to represent the relationship between two other tables in a database when the relationship is many-to-many.

Composite Key

A key composed of more than one attribute (column) in a table that uniquely identifies a row.

Foreign Key

A column in a table that references the primary key of another table. It establishes relationships among tables in a database.

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Primary Key

A unique identifier for each row in a table.

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Database Table

A structured form of data storage, organized into rows and columns.

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Specialization/Generalization

A way to categorize data that involves a hierarchy of categories. One entity is the base, and the others are subtypes.

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Aggregate

A way to group related data.

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Relational Model

A database model that organizes data into tables with rows and columns, where relationships between data are defined through keys.

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Database Diagram

A visual representation of the structure of a database, showing tables, columns, relationships, and keys.

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Overlapping Specialization

A type of specialization where subtypes can share common attributes and instances can belong to multiple subtypes simultaneously.

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Unary Relationship

A relationship where an entity relates to itself, creating a loop within the same type of data.

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Disjoint Specialization

A type of specialization where subtypes have distinct attributes and instances can belong to only one subtype.

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Multi-valued Attribute

An attribute that can have multiple values for a single instance of an entity.

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How to Implement Multi-valued Attributes?

To store multiple values for an attribute, create a separate table with a foreign key referencing the primary key of the main table.

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One-to-One Relationship

A relationship where one record in a table is linked to only one record in another table.

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Shared Email Attribute

In multi-valued attributes, if the emails can be shared, use one table for all emails.

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Non-shared Email Attribute

In multi-valued attributes, if the emails cannot be shared, use a separate table for each individual's emails.

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Entity Relationship Diagram (ERD)

A visual representation of the entities and relationships within a database.

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Study Notes

Database Design

  • A database design involves creating structures for storing and managing data efficiently.
  • Various data models exist (Network, Hierarchical, Relational, Object-Oriented).
  • The Relational Model is prevalent in commercial data processing.
  • A relation is essentially a table.

Relational Model

  • Tables (relations) are composed of rows (tuples) and columns (attributes).
  • Each cell in a table holds a single atomic value.
  • Attributes have distinct names and values from the same domain.
  • Relation names are unique.

Keys

  • Relational Keys are critical for identifying and linking data.
  • Several key types exist: Primary Keys, Composite Keys, Candidate Keys, Super Keys, and Foreign Keys.
    • Primary Keys: Uniquely identify each row/tuple in a relation. They are a minimal set of attributes that guarantees unique rows.
    • Composite Keys: Primary keys composed of multiple attributes. Essential for relations where single attribute isn't sufficient.
    • Candidate Keys: All possible candidates to be chosen as primary keys (unique).
    • Super Keys: Any set of attributes that uniquely identifies each row in the table. Includes all Candidate Keys.
    • Foreign Keys: Attributes in one table that reference the primary key in another, linking relations.

Relationships

  • Relationships between tables are vital. They connect data from different tables.
  • One-to-One (1:1): One record in one table can link to at most one record in another. -The primary key of one table is used as a foreign key in the other.
  • One-to-Many (1:N/1:M): One record in one table can link to many records in another. -The primary key of the "one" table is used as a foreign key in the "many" table.
  • Many-to-Many (M:N/M:N): Many records in one table can link to many records in another. -A third intermediate/associative table is used, with each parent table's primary key as a foreign key.

Integrity Rules

  • Integrity rules ensure data accuracy and consistency.
    • Entity Integrity: Primary key values cannot be null. Every row must be identifiable. -A primary key must have at least one value.
    • Referential Integrity: Foreign keys must either match a primary key in another table, or be null. This ensures consistency in linked tables between relations, by using a foreign key on the weaker side.

Multi-Valued Attributes

  • Handling attributes with multiple values: Create related separate tables (usually for non-shared data).
  • Foreign keys help link these related tables.

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Description

This quiz focuses on the principles of database design, particularly emphasizing the relational model. It covers various data models, the importance of relational keys, and the structure of tables in a database. Test your understanding of how data is managed efficiently.

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