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 the Third Normal Form (3NF)?

  • It must not contain any non-prime attributes.
  • It must be in Second Normal Form (2NF). (correct)
  • It must have at least two candidate keys.
  • It must have a composite primary key.

    • Which of the following statements correctly describes transitive partial dependency?

  • It occurs when non-key attributes depend on another non-key attribute. (correct)
  • It is when all attributes are fully dependent on the primary key.
  • It signifies a one-to-many relationship between two tables.
  • It is a relationship where non-key attributes depend on only a part of a composite key.

    • In the context of normalization, what defines a prime attribute?

  • Any attribute that is not part of any candidate key.
  • An attribute that can exist independently of others.
  • An attribute that directly relates to the primary key.
  • An attribute that is part of any candidate key. (correct)

    • What is the primary goal of achieving Second Normal Form (2NF)?

    <p>To ensure that all non-key attributes are fully functional dependent on the primary key.</p> Signup and view all the answers

    Which of the following could lead to a table violating the Second Normal Form (2NF)?

    <p>An attribute that depends on only a part of the composite primary key.</p> Signup and view all the answers

    Which statement correctly defines a primary key?

    <p>It uniquely identifies each record in a table.</p> Signup and view all the answers

    What is an example of a composite key?

    <p>Two or more columns combined to form a unique identifier.</p> Signup and view all the answers

    Which statement about a foreign key is true?

    <p>It establishes a link between two different tables.</p> Signup and view all the answers

    What type of dependency occurs when a non-primary attribute is defined by another non-primary attribute?

    <p>Transitive Dependency</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a primary key?

    <p>They can link to other tables as foreign keys.</p> Signup and view all the answers

    In the context of relational databases, which statement about candidate keys is correct?

    <p>Any candidate key can be composed of multiple columns.</p> Signup and view all the answers

    What does the term 'NULL values' imply in relation to primary keys?

    <p>They prevent unique identification.</p> Signup and view all the answers

    How can multiple rows be uniquely identified using a composite key?

    <p>By combining unique attributes from different columns.</p> Signup and view all the answers

    What does a functional dependency of the form X→Y signify in a database table?

    <p>X is an attribute that determines Y's value</p> Signup and view all the answers

    In the context of database normalization, which of the following is NOT a purpose of functional dependencies?

    <p>To increase data redundancy</p> Signup and view all the answers

    Which statement accurately describes full dependency in a database?

    <p>All attributes of the primary key are needed to identify a non-primary attribute's value</p> Signup and view all the answers

    What is a characteristic of partial dependency in a database table?

    <p>It can be resolved using normalization techniques</p> Signup and view all the answers

    Which statement is true regarding the primary key in a table with the attributes roll_no, name, and city?

    <p>roll_no is the only unique attribute and serves as the primary key</p> Signup and view all the answers

    What does achieving a higher normal form, like BCNF, help prevent in a database?

    <p>Data inconsistency and redundancy</p> Signup and view all the answers

    Which statement about a Super Key is true?

    <p>A Super Key uniquely identifies all attributes in a relation.</p> Signup and view all the answers

    Which of the following is NOT a level of normalization typically referenced?

    <p>Recursive Normal Form (RNF)</p> Signup and view all the answers

    What is the purpose of database normalization?

    <p>To organize data in a consistent way.</p> Signup and view all the answers

    In which scenario would a database designer focus on achieving the Second Normal Form (2NF)?

    <p>When partial dependencies are present with a composite key</p> Signup and view all the answers

    What criterion does a relation need to satisfy to be in Second Normal Form (2NF)?

    <p>It must be in First Normal Form (1NF) and have no partial dependency.</p> Signup and view all the answers

    What defines a primary key in a relational database?

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

    Which of the following describes the First Normal Form (1NF)?

    <p>It requires atomicity and a primary key.</p> Signup and view all the answers

    Which of the following forms is a prerequisite for a table to be in Third Normal Form (3NF)?

    <p>The table must have been designed in 2NF.</p> Signup and view all the answers

    What typically results from effective database normalization?

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

    Which of the following statements correctly describes composite keys?

    <p>Composite keys are used to identify records based on multiple attributes.</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 improves data integrity and reduces undesirable effects of insertion, deletion, or updates.

    Functional Dependencies

    • Functional dependency is a relationship between attribute sets in a table.
    • It describes how the value of one attribute determines another's value.
    • Represented as X → Y, where X and Y are attribute sets in a table.

    Functional Dependencies Example

    • A table "Employees" with attributes (employee ID, name, department, salary).
    • "department → salary" means employees in the same department share the same salary.

    Another Example

    • 'roll_no' is a unique identifier (primary key) for a student table.
    • 'name' and 'city' depend on 'roll_no'
    • 'name' and 'city' are functionally dependent on 'roll_no'.
    • You cannot get 'roll_no' based on 'name' or 'city' alone.

    Why Functional Dependency Is Used?

    • Maintains data integrity
    • Facilitates easy data maintenance
    • Enables efficient data storage
    • Improves data redundancy

    Types of Dependencies

    • Full Dependency: All primary key attributes are needed to determine a non-primary attribute. Example: To get a student's mark, both roll number and subject ID are needed.

    • Partial Dependency: Primary key is composed of multiple attributes; a non-key attribute depends on only part of the composite key. Example: In a student table, if we use roll number + subject ID, but a subject name only depends on the subject ID, then it's a partial dependency.

    • Transitive Dependency: The value of a non-primary attribute is determined by another non-primary attribute. Example: If 'city' is dependent on 'zip_code', which is also not a primary key, then there is transitive dependency.

    Primary Key

    • Uniquely identifies each row in a table.
    • Cannot contain NULL values.
    • Example: 'STUD_NO' in a 'STUDENTS' table.

    Foreign Key

    • A column or set of columns referencing a primary key in another table, creating a link between them.
    • Example: 'STUD_NO' in a 'STUDENT_COURSE' table references 'STUD_NO' in a 'STUDENT' table.

    Composite Key

    • Combination of two or more columns uniquely identifying each row.
    • Example: 'STUD_NO' and 'PHONE' together uniquely define a student.

    Super Key

    • An attribute (or set of attributes) uniquely defining all attributes in a relation.
    • It can include more than one candidate key.
    • Example: If 'ID' and ('First Name', 'Last Name') are both candidate keys in a 'STUDENT' table, both together are a super key.

    Database Normalization

    • Database normalization is a database design principle for organizing data consistently to avoid complexities and redundancy.

    Purpose of Normalization

    • To avoid complexities
    • To eliminate redundancy
    • To organize data consistently.
    • Primary, foreign, and composite keys support these relationships.

    1NF, 2NF and 3NF

    • 1NF, 2NF and 3NF are the first three types of database normalization steps. They stand for first normal form, second normal form, and third normal form, respectively.
    • Other higher normal forms (4NF, 5NF) exist but are less commonly used by DB administrators
    • Subsequent normal forms build upon previous ones.

    The First Normal Form - 1NF

    • A table is in 1NF if it meets atomicity (no single cell holds more than one value) and has a primary key for identification.

    The Second Normal Form - 2NF

    • A table is in 2NF if it's already in 1NF, with no partial dependencies (non-key attributes depend on the entire primary key, not just part of it).

    The Third Normal Form - 3NF

    • A table is in 3NF if it's in 2NF and has no transitive dependencies (non-key attributes don't depend on other non-key attributes).

    BCNF (Boyce-Codd Normal Form)

    • A stronger form than 3NF: if a functional dependency X --> A exists, then X must be a superkey.
    • Each normal form builds on the previous one, with each new level being more strict.

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    Related Documents

    Database Normalization Lecture 2 PDF

    Description

    This quiz explores the principles of database normalization and functional dependencies. You'll learn how to organize data effectively and understand the relationships between attributes in a database. Test your understanding with practical examples and applications.

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