Database Normalization and Functional Dependencies
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Database Normalization and Functional Dependencies

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Questions and Answers

What is a requirement for a table to be in Third Normal Form (3NF)?

  • It must consist only of prime attributes.
  • It must eliminate all functional dependencies.
  • It must be in Second Normal Form (2NF) and remove transitive partial dependency. (correct)
  • It must have at least two candidate keys.

    • In database normalization, which Normal Form primarily focuses on eliminating partial dependencies?

  • Third Normal Form (3NF)
  • Boyce-Codd Normal Form (BCNF)
  • First Normal Form (1NF)
  • Second Normal Form (2NF) (correct)

    • Which statement is true regarding candidate keys?

  • A candidate key is always a super key. (correct)
  • Every attribute in a candidate key is a non-prime attribute.
  • Candidate keys must include a foreign key.
  • A candidate key can consist of multiple non-prime attributes.

    • What does the elimination of transitive dependencies in 3NF ensure?

    <p>No attribute depends on another non-key attribute.</p> Signup and view all the answers

    Which of the following scenarios would represent a violation of the rules of 2NF?

    <p>A table where an attribute depends on only part of a composite primary key.</p> Signup and view all the answers

    What is a super key in a database?

    <p>A set of attributes that can uniquely identify a row in a table.</p> Signup and view all the answers

    What does normalization primarily aim to achieve in a database?

    <p>Reduce data integrity issues.</p> Signup and view all the answers

    Which statement describes the First Normal Form (1NF)?

    <p>It enforces that each column contains atomic values.</p> Signup and view all the answers

    What characterizes the Second Normal Form (2NF)?

    <p>It has no partial dependency of any column on the primary key.</p> Signup and view all the answers

    Which condition must be satisfied for a relation to be in Third Normal Form (3NF)?

    <p>No transitive dependencies exist among attributes.</p> Signup and view all the answers

    What is a primary key in a database?

    <p>A single attribute that uniquely identifies each record in a table.</p> Signup and view all the answers

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

    <p>To ensure referential integrity between two tables.</p> Signup and view all the answers

    Why is eliminating data redundancy important in database design?

    <p>It ensures that there are no duplicate entries for the same data.</p> Signup and view all the answers

    What defines a Super Key in a database?

    <p>A set of attributes that can potentially identify tuples in a relation.</p> Signup and view all the answers

    Which statement best describes the purpose of database normalization?

    <p>To organize data and eliminate redundancy.</p> Signup and view all the answers

    Which of the following is NOT a criterion for a table to be in First Normal Form (1NF)?

    <p>All data must be stored in chronological order.</p> Signup and view all the answers

    Which condition is essential for a table to meet the criteria of Second Normal Form (2NF)?

    <p>The table must be in First Normal Form.</p> Signup and view all the answers

    What is the function of a primary key in a database?

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

    Which of the following attributes constitutes a candidate key?

    <p>A set of attributes that can uniquely identify records.</p> Signup and view all the answers

    How does normalization help in eliminating data redundancy?

    <p>By creating relationships that reduce duplicate data storage.</p> Signup and view all the answers

    What is a distinguishing feature of Third Normal Form (3NF)?

    <p>It eliminates all transitive dependencies.</p> Signup and view all the answers

    Study Notes

    Database Normalization

    • Database normalization is a design principle for organizing data consistently and avoiding redundancy.
    • It enhances data integrity.
    • It reduces the undesirable characteristics associated with data insertion, deletion, and updates.

    Functional Dependencies

    • A functional dependency is a relationship between two sets of attributes in a database table (how one attribute determines another).
    • It's represented as X → Y, where X and Y are sets of attributes.
    • Example: In an "Employees" table, "department → salary" means that employees with the same department have the same salary.

    Functional Dependency Example

    • This example illustrates how functional dependencies determine attribute values.
    • In an employee table, employee ID, name, department, and salary, the department determines the salary for employees in the same department.

    Another Example

    • Example illustrating how attributes depend on a primary key.
    • "roll_no" is the unique identifier, and "name" and "city" depend on "roll_no" to uniquely identify student details.

    Why Functional Dependency is Used

    • It maintains data integrity.
    • Simplifies data maintenance.
    • Improves data storage efficiency.
    • Reduces data redundancy by avoiding duplicate records.

    Types of Dependencies

    Full Dependency

    • All attributes of the primary key are needed to identify a non-primary attribute.
    • Example: Requires both roll number and subject to determine the mark

    Partial Dependency

    • A primary key with more than one attribute leads to a partial dependency.
    • Example: multiple "roll_nos" can have the same "sub_id" making it a composite key. "roll_no + sub_id" is crucial to determine other related values.

    Transitive Dependency

    • The value of a non-primary attribute is determined by another non-primary attribute.
    • Example: Identifying a city by the zip-code (where city and zip-code aren't part of the primary key).

    Primary Key

    • A primary key uniquely identifies each record in a table.
    • Example: "stud_no" in a student table is a primary key, ensuring each student ID is unique.
    • A primary key cannot have NULL values.

    Foreign Key

    • A foreign key in one table links to a primary key in another table.
    • Example: "stud_no" in a "student_course" table is a foreign key and links to the "student" table's "stud_no" primary key.

    Composite Key

    • A composite key is a combination of two or more columns that uniquely identifies a row in a table.
    • Example: Combining "stud_no" and "stud_phone" to create a composite key, uniquely identifying each student record.

    Super Key

    • A superkey is an attribute (or set of attributes) that uniquely defines all the attributes in a relation.
    • It can include more than one candidate key.
    • Example: A student's ID, first name, last name, age, gender, and phone number.

    Database Normalization

    • Database normalization is a process to organize data in a relational database to reduce data redundancy, improve data integrity, and avoid anomalies during data insertion, updating, and deletion.

    Purpose of Normalization

    • Avoid complexity.
    • Eliminate duplicates.
    • Organize data consistently.
    • Database administrators use primary, foreign, and composite keys to achieve and maintain relationships.

    1NF, 2NF and 3NF

    • 1NF (First Normal Form): No repeating groups of data, each field should contain only atomic values.
    • 2NF (Second Normal Form): 1NF, and all non-key attributes are fully functionally dependent on the primary key
    • 3NF (Third Normal Form): 2NF, and no transitive functional dependencies (non-key attributes depend on other non-key attributes)

    The First Normal Form (1NF)

    • A table is in 1NF if it meets specific criteria.
    • It has atomic data, and a primary key.

    The Second Normal Form (2NF)

    • A 2NF table is in 1NF, and all non-key attributes are fully dependent on the entire primary key, not just part of it. No partial dependencies.

    The Third Normal Form (3NF)

    • 3NF is based on 2NF with no transitive partial dependencies (non-key attributes don't depend on other non-key attributes). The table is in 3NF when it is in 2NF and there are no transitive dependencies.

    BCNF (Boyce-Codd Normal Form)

    • A stronger form of 3NF, dealing with a more strict dependency rule. Every determinant in a table must be a candidate key.

    General Normal Form Definitions

    • Define prime and non-prime attributes considering multiple candidate keys.

    Normal Forms Defined Informally

    • 1NF: All attributes depend on the key.
    • 2NF: All attributes depend on the whole key.
    • 3NF: All attributes depend on nothing but the key.

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    Related Documents

    Database Normalization Lecture 2 PDF

    Description

    This quiz covers the principles of database normalization and the concept of functional dependencies. It explains how to organize data efficiently, ensure data integrity, and establish relationships between attributes in a database. Examples are provided to illustrate these key concepts.

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