DCIT 55 - Relational Database Concepts Review
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Questions and Answers

What is a common misconception about strong relationships in the context of databases?

  • It is primarily based on the quantity of data stored (correct)
  • It always involves a one-to-one relationship
  • It doesn't help in establishing connections between tables
  • It is unrelated to primary keys

    • In the ER Model, what does cardinality express?

  • The maximum number of entities associated with one occurrence of the related entity (correct)
  • The type of data stored in the database
  • The size of the database
  • The number of data attributes in the database

    • Which component is NOT considered one of the three basic notions of the ER Model?

  • Entities
  • Attributes
  • Relationships
  • Cardinality (correct)

    • What is a common misconception about the main parts of a database system?

    <p>Hardware is the most crucial part</p> Signup and view all the answers

    Which of the following is NOT one of the nine functions of a Database Management System (DBMS)?

    <p>Query performance optimization</p> Signup and view all the answers

    What type of attributes can have only a single value?

    <p>Single-Valued Attributes</p> Signup and view all the answers

    What is the purpose of a Project operation in a database?

    <p>Yields a vertical subset of a table</p> Signup and view all the answers

    What is the main function of an ER diagram in a database system?

    <p>It represents a conceptual database viewed by an end-user</p> Signup and view all the answers

    What characterizes a single-user database?

    <p>Supports only one user at a time</p> Signup and view all the answers

    What is a Transaction in the context of a database?

    <p>A set of operations that performs a particular task</p> Signup and view all the answers

    What is the significance of a Centralized database?

    <p>Supports data located at a single site</p> Signup and view all the answers

    What is a Primary Key?

    <p>An attribute that uniquely identifies any given entity</p> Signup and view all the answers

    What is the purpose of a SAVEPOINT in database transactions?

    <p>To mark and save the current point in the processing of a transaction</p> Signup and view all the answers

    In database terminology, what does the term 'Domain' refer to?

    <p>An attribute's set of possible values</p> Signup and view all the answers

    What does the Implicit Commit Command do in the context of databases?

    <p>Forces a COMMIT to occur automatically without user intervention</p> Signup and view all the answers

    What is Connectivity in databases?

    <p>A command used to describe the relationship classification</p> Signup and view all the answers

    What is the purpose of the Relational Model in database management?

    <p>To enable programmers to view data logically rather than physically</p> Signup and view all the answers

    What type of anomaly occurs when entering new records?

    <p>Insertion anomalies</p> Signup and view all the answers

    What is the purpose of the ROLLBACK command in a database system?

    <p>Terminate the current transaction and undo changes</p> Signup and view all the answers

    What does the Natural join do when linking tables?

    <p>Selects rows with common values in common attribute(s)</p> Signup and view all the answers

    What is the definition of a Super key in a database context?

    <p>Any attribute that identifies rows uniquely</p> Signup and view all the answers

    In a multiple-user database system, what does the abbreviation TCL stand for?

    <p>Transaction Control Language</p> Signup and view all the answers

    How does the Equijoin link tables together?

    <p>By comparing specified columns with an equality condition</p> Signup and view all the answers

    Study Notes

    ER Model and Relationships

    • Strong relationships exist when the PK of the related entity contains the PK component of the parent entity.
    • Weak relationships exist if the PK of the related entity does not contain the PK component of the parent entity.
    • Existence dependence exists in the database only when it is associated with another related entity occurrence.
    • Existence independence is an entity that can exist apart from one or more related entities.

    Database System Components

    • Five main parts of a database system:
      • Data
      • People
      • Hardware
      • Software
      • Process

    Relational Algebra Operators

    • Eight relational algebra operators:
      • Union
      • Intersect
      • Difference
      • Divide
      • Product
      • Select
      • Join
      • Project

    Database Management System (DBMS)

    • Nine functions of DBMS:
      • Data dictionary management
      • Data storage management
      • Data transformation and presentation
      • Security management
      • Multiuser access control
      • Backup and recovery management
      • Data integrity management
      • Database access languages and application programming interfaces
      • Database communication interfaces

    Database Concepts

    • Primary key: an attribute that uniquely identifies any given entity.
    • Composite key: composed of more than one attribute.
    • Foreign key: an attribute whose values match primary key values in the related table.
    • Secondary key: key used strictly for data retrieval purposes.
    • Candidate key: a superkey without redundancies.
    • Super key: any key that uniquely identifies each row.

    Data and Information

    • Data: raw material used to derive information.
    • Information: a product derived from data.

    Database Operations

    • Transaction: a set of database operations that performs a particular task.
    • COMMIT: used to permanently save any transaction into the database.
    • SAVEPOINT: marks and saves the current point in the processing of a transaction.
    • ROLLBACK: terminates the current transaction and undoes any changes made during the transaction.

    Join Operations

    • Natural join: links tables by selecting only rows with common values in their common attribute(s).
    • Theta join: applicable if any other comparison operator is used.
    • Equijoin: links tables on the basis of an equality condition that compares specified columns of each table.
    • Outer join: the matched pairs are retained, and any unmatched values in the other table are left null.

    Data Warehouse and Database

    • Database: a collection of interrelated data.
    • Data warehouse: stores data used to generate information required to make tactical or strategic decisions.

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    Description

    Test your knowledge of Relational Database Concepts including ER model, attributes, anomalies, and database types with this quiz. Topics include ER diagrams, derived/computed attributes, single-valued attributes, multivalued attributes, deletion anomalies, single-user databases, and transactions.

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