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Questions and Answers
What is a requirement for a table to be in the Third Normal Form (3NF)?
What is a requirement for a table to be in the Third Normal Form (3NF)?
Which of the following statements correctly describes transitive partial dependency?
Which of the following statements correctly describes transitive partial dependency?
In the context of normalization, what defines a prime attribute?
In the context of normalization, what defines a prime attribute?
What is the primary goal of achieving Second Normal Form (2NF)?
What is the primary goal of achieving Second Normal Form (2NF)?
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Which of the following could lead to a table violating the Second Normal Form (2NF)?
Which of the following could lead to a table violating the Second Normal Form (2NF)?
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Which statement correctly defines a primary key?
Which statement correctly defines a primary key?
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What is an example of a composite key?
What is an example of a composite key?
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Which statement about a foreign key is true?
Which statement about a foreign key is true?
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What type of dependency occurs when a non-primary attribute is defined by another non-primary attribute?
What type of dependency occurs when a non-primary attribute is defined by another non-primary attribute?
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Which of the following is NOT a characteristic of a primary key?
Which of the following is NOT a characteristic of a primary key?
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In the context of relational databases, which statement about candidate keys is correct?
In the context of relational databases, which statement about candidate keys is correct?
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What does the term 'NULL values' imply in relation to primary keys?
What does the term 'NULL values' imply in relation to primary keys?
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How can multiple rows be uniquely identified using a composite key?
How can multiple rows be uniquely identified using a composite key?
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What does a functional dependency of the form X→Y signify in a database table?
What does a functional dependency of the form X→Y signify in a database table?
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In the context of database normalization, which of the following is NOT a purpose of functional dependencies?
In the context of database normalization, which of the following is NOT a purpose of functional dependencies?
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Which statement accurately describes full dependency in a database?
Which statement accurately describes full dependency in a database?
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What is a characteristic of partial dependency in a database table?
What is a characteristic of partial dependency in a database table?
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Which statement is true regarding the primary key in a table with the attributes roll_no, name, and city?
Which statement is true regarding the primary key in a table with the attributes roll_no, name, and city?
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What does achieving a higher normal form, like BCNF, help prevent in a database?
What does achieving a higher normal form, like BCNF, help prevent in a database?
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Which statement about a Super Key is true?
Which statement about a Super Key is true?
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Which of the following is NOT a level of normalization typically referenced?
Which of the following is NOT a level of normalization typically referenced?
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What is the purpose of database normalization?
What is the purpose of database normalization?
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In which scenario would a database designer focus on achieving the Second Normal Form (2NF)?
In which scenario would a database designer focus on achieving the Second Normal Form (2NF)?
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What criterion does a relation need to satisfy to be in Second Normal Form (2NF)?
What criterion does a relation need to satisfy to be in Second Normal Form (2NF)?
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What defines a primary key in a relational database?
What defines a primary key in a relational database?
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Which of the following describes the First Normal Form (1NF)?
Which of the following describes the First Normal Form (1NF)?
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Which of the following forms is a prerequisite for a table to be in Third Normal Form (3NF)?
Which of the following forms is a prerequisite for a table to be in Third Normal Form (3NF)?
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What typically results from effective database normalization?
What typically results from effective database normalization?
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Which of the following statements correctly describes composite keys?
Which of the following statements correctly describes composite keys?
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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
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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.
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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.
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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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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.
