Database Concept and Design: Data Redundancies
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Questions and Answers

What is the primary goal of normalization in database design?

  • To increase data storage
  • To enhance data security
  • To improve data integrity
  • To reduce data redundancy (correct)

    • A repeating group in a relational table is allowed in database design.

    False

    What is the purpose of a dependency diagram?

    To depict all dependencies and relationships among table attributes

    The primary key in a relational table can be an attribute or a combination of _______________________.

    <p>attributes</p> Signup and view all the answers

    What is the second normal form (2NF) in database design?

    <p>Eliminating partial dependencies</p> Signup and view all the answers

    Surrogate keys are used when primary keys are suitable.

    <p>False</p> Signup and view all the answers

    Match the following database design concepts with their descriptions:

    <p>1NF = Eliminating repeating groups 2NF = Eliminating partial dependencies 3NF = Eliminating transitive dependencies Normalization = Improving data integrity and reducing data redundancies</p> Signup and view all the answers

    What is the importance of improving data granularity in database design?

    <p>To ensure accurate and precise data representation</p> Signup and view all the answers

    The process of eliminating transitive dependencies is part of _______________________.

    <p>3NF</p> Signup and view all the answers

    Normalization is a sufficient condition for good database design.

    <p>False</p> Signup and view all the answers

    What is the characteristic of fully functional dependence?

    <p>Attribute C is functionally dependent on a composite key AB but not on any subset of that composite key</p> Signup and view all the answers

    Partial dependency occurs when the determinant is the entire primary key.

    <p>False</p> Signup and view all the answers

    What is the first step in converting a table to First Normal Form?

    <p>Eliminate the repeating groups</p> Signup and view all the answers

    Attribute A determines attribute B if all the rows in the table that agree in value for attribute A also agree in value for attribute ____________________.

    <p>B</p> Signup and view all the answers

    Match the type of functional dependency with its description:

    <p>Partial dependency = Exists when the determinant is only part of the primary key Transitive dependency = Exists when there are functional dependencies such that X → Y, Y → Z, and X is the primary key Fully functional dependence = Attribute C is functionally dependent on a composite key AB but not on any subset of that composite key</p> Signup and view all the answers

    What is the purpose of converting a table to First Normal Form?

    <p>All of the above</p> Signup and view all the answers

    In transitive dependency, X is not the primary key.

    <p>False</p> Signup and view all the answers

    What is the main purpose of identifying functional dependencies in a database?

    <p>To prevent anomalies</p> Signup and view all the answers

    What is the main objective of normalization in database design?

    <p>To minimize data redundancies</p> Signup and view all the answers

    The highest level of normalization is always most desirable.

    <p>False</p> Signup and view all the answers

    What are the three types of anomalies that can occur in a database?

    <p>Update anomaly, Delete anomaly, Insert anomaly</p> Signup and view all the answers

    Functional dependence exists when the attribute B is fully dependent on the attribute ___________.

    <p>A</p> Signup and view all the answers

    Match the following normal forms with their descriptions:

    <p>1NF = Eliminates repeating groups in a table 2NF = Ensures that each non-prime attribute depends on the entire primary key 3NF = Eliminates transitive dependencies in a table</p> Signup and view all the answers

    What is the benefit of using a relational database environment?

    <p>Helping designers avoid data integrity problems</p> Signup and view all the answers

    Normalization is necessary only during database design.

    <p>False</p> Signup and view all the answers

    The structure of a database table can be improved through _______________________.

    <p>normalization</p> Signup and view all the answers

    What is the purpose of analyzing entity-attribute relationships in database design?

    <p>To determine if the structure can be improved</p> Signup and view all the answers

    What is the result of de-normalization?

    <p>Increased performance but greater data redundancy</p> Signup and view all the answers

    Study Notes

    Database Concept and Design

    • A repeating group is a group of multiple entries of the same type that can exist for any single key attribute, which proves the presence of data redundancies; relational tables must not contain repeating groups.
    • Identifying primary keys is essential, and they can be an attribute or a combination of attributes.

    Conversion to First Normal Form

    • Step 1: Eliminate the repeating groups
    • Step 2: Identify the primary key
    • Use a dependency diagram to depict all dependencies among table attributes, which helps to get an overview of all relationships and makes it less likely that an important dependency will be overlooked.

    Normalization

    • Normalization is a process for evaluating and correcting table structures to minimize data redundancies, which reduces data anomalies.
    • Normalization involves a series of stages called normal forms: First Normal Form (1NF), Second Normal Form (2NF), and Third Normal Form (3NF).
    • 2NF is better than 1NF, and 3NF is better than 2NF, but the highest level of normalization is not always desirable.
    • De-normalization produces a lower normal form, which increases performance but increases data redundancy.

    The Need for Normalization

    • Normalization eliminates anomalies, ensures data consistency, and is used while designing and re-designing a database structure.
    • It analyzes the relationship among the attributes within each entity and determines if the structure can be improved.

    Anomalies

    • Update anomaly
    • Delete anomaly
    • Insert anomaly

    Normalization Process

    • The objective is to ensure that each table conforms to the concept of well-formed relations.
    • Each table represents a single subject, and no data item is unnecessarily stored in more than one table.
    • All nonprime attributes in a table are dependent on the primary key, and each table is void of insertion, update, and deletion anomalies.

    Functional Dependence Concepts

    • Functional dependence: The attribute B is fully functionally dependent on the attribute A if each value of A determines one and only one value of B.
    • Fully functional dependence: Attribute A determines attribute B if all of the rows in the table that agree in value for attribute A also agree in value for attribute B.

    Types of Functional Dependencies

    • Partial dependency: A functional dependence in which the determinant is only part of the primary key.
    • Transitive dependency: A functional dependence where X → Y, Y → Z, and X is the primary key.

    Conversion to Second and Third Normal Forms

    • Conversion to Second Normal Form:
      • Step 1: Make new tables to eliminate partial dependencies.
      • Step 2: Reassign corresponding dependent attributes.
    • Conversion to Third Normal Form:
      • Step 1: Make new tables to eliminate transitive dependencies.
      • Step 2: Reassign corresponding dependent attributes.

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    Related Documents

    06 Normalizing Database Designs â Part 1.pdf

    Description

    This quiz covers concepts related to data redundancies in relational tables, including repeating groups and occurrence.

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