Understanding DBMS Keys and Dependencies

What distinguishes a candidate key from a primary key?

• A candidate key can be any unique identifier, while a primary key is the selected candidate key used for record identification.

• A primary key can be any unique identifier, while a candidate key is the selected primary key.

• A candidate key must always be a single attribute, while a primary key can be composite.

• A primary key is used for foreign key relationships, while a candidate key is not.

Explain the concept of functional dependency in DBMS.

• Functional dependency is a method to store data in multiple tables without any relationships.

• Functional dependency means that all attributes are independent of each other.

• Functional dependency is a relationship where one attribute's value determines another attribute's value in a database.

• Functional dependency refers to the process of normalizing a database by removing all attributes.

How do you calculate the attribute closure of a set of attributes?

• The attribute closure is the set of all attributes that can be functionally determined by the given set of attributes.

• The attribute closure is the set of all attributes in the database.

• The attribute closure is determined by the number of attributes in the set.

• You can calculate the attribute closure by listing all possible values.

Describe the relationship between functional dependencies and candidate keys.

• Functional dependencies are irrelevant to candidate keys.

• Candidate keys can exist without any functional dependencies.

• Functional dependencies only apply to primary keys, not candidate keys.

• Functional dependencies help identify candidate keys by showing which attributes can uniquely determine others.

What is the difference between a super key and a candidate key?

• A super key can have extra attributes, while a candidate key is minimal.

• A super key is always a primary key, while a candidate key is not.

• A super key is a combination of all attributes in a table, while a candidate key is a single attribute.

• A candidate key can have duplicate values, while a super key cannot.

How can you identify candidate keys using functional dependencies?

• Candidate keys are always the primary keys of the table.

• Candidate keys can be identified by finding minimal attribute sets whose closures include all attributes.

• Candidate keys can be found by grouping all attributes together without considering dependencies.

• Candidate keys can be identified by selecting any single attribute from the set.

What are the implications of foreign key constraints on data integrity?

• Foreign key constraints allow duplicate records in the database.

• Foreign key constraints have no effect on data relationships.

• Foreign key constraints can be ignored without consequences.

• Foreign key constraints enhance data integrity by enforcing referential integrity and preventing orphaned records.

What is the role of composite keys in a relational database?

• Composite keys uniquely identify records in a table using multiple columns.

• Composite keys are a type of data encryption method.

• Composite keys are only used in NoSQL databases.

• Composite keys are used to store images in a database.

Explain how to derive functional dependencies from a given set of attributes.

• Functional dependencies can be determined by random selection of attributes.

• Functional dependencies are derived solely from the number of attributes present.

• Functional dependencies can be derived by analyzing attribute relationships and determining if one attribute can uniquely determine another.

• Functional dependencies are irrelevant to attribute relationships.

What is the importance of normalization in relation to keys and dependencies?

• Normalization eliminates the need for keys in a database.

• Normalization increases data duplication and inconsistency.

• Normalization is only relevant for large datasets and not for small ones.

• Normalization is important for establishing clear relationships between keys and dependencies, ensuring data integrity and reducing redundancy.