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What is the main function of a foreign key constraint in a one-to-one relationship?
What is the main function of a foreign key constraint in a one-to-one relationship?
What happens if a unique constraint is not applied to the foreign key in a one-to-one relationship?
What happens if a unique constraint is not applied to the foreign key in a one-to-one relationship?
Which statement correctly describes the role of a composite primary key in a one-to-one relationship?
Which statement correctly describes the role of a composite primary key in a one-to-one relationship?
How does placing a unique constraint on both foreign keys in a one-to-one relationship affect data integrity?
How does placing a unique constraint on both foreign keys in a one-to-one relationship affect data integrity?
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Why is a unique constraint essential in a one-to-one relationship between the Student and Advisor tables?
Why is a unique constraint essential in a one-to-one relationship between the Student and Advisor tables?
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What is a potential issue if referential integrity is not enforced in a relational database?
What is a potential issue if referential integrity is not enforced in a relational database?
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In which case would inserting a record lead to an insertion anomaly in a one-to-one relationship?
In which case would inserting a record lead to an insertion anomaly in a one-to-one relationship?
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What would be the consequence of having a foreign key that is not unique in a one-to-one relationship?
What would be the consequence of having a foreign key that is not unique in a one-to-one relationship?
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What is a defining characteristic of a superkey?
What is a defining characteristic of a superkey?
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How does a candidate key differ from a superkey?
How does a candidate key differ from a superkey?
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Which statement is true about primary keys in a relational database?
Which statement is true about primary keys in a relational database?
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When a table has multiple candidate keys, which is selected as the primary key?
When a table has multiple candidate keys, which is selected as the primary key?
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If a superkey {A, B, C} is given, which of the following could represent a valid candidate key?
If a superkey {A, B, C} is given, which of the following could represent a valid candidate key?
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Can a foreign key function as a primary key within the same relation?
Can a foreign key function as a primary key within the same relation?
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Which of the following properties is essential for every primary key in a relational database?
Which of the following properties is essential for every primary key in a relational database?
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What is the primary purpose of a candidate key?
What is the primary purpose of a candidate key?
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What ensures that every employee must have an associated department in the Employee table?
What ensures that every employee must have an associated department in the Employee table?
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If a foreign key allows NULL values, what is a likely consequence in terms of participation?
If a foreign key allows NULL values, what is a likely consequence in terms of participation?
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Which of the following best defines total participation in the context of relational databases?
Which of the following best defines total participation in the context of relational databases?
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In the Employee table, what does the foreign key refer to?
In the Employee table, what does the foreign key refer to?
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Which statement accurately describes the implications of a foreign key with a NOT NULL constraint?
Which statement accurately describes the implications of a foreign key with a NOT NULL constraint?
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What role does the CHECK constraint play in the definition of the foreign key?
What role does the CHECK constraint play in the definition of the foreign key?
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What happens to an employee's record if their Department_ID does not have a corresponding entry in the Department table?
What happens to an employee's record if their Department_ID does not have a corresponding entry in the Department table?
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Which constraint combination ensures that no employee record can exist without a valid department association?
Which constraint combination ensures that no employee record can exist without a valid department association?
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What is the primary purpose of a unique constraint in a one-to-one relationship?
What is the primary purpose of a unique constraint in a one-to-one relationship?
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Which approach ensures that an employee can be assigned only one parking space in a database?
Which approach ensures that an employee can be assigned only one parking space in a database?
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What could happen if no unique constraint is applied to the foreign key in a one-to-one relationship?
What could happen if no unique constraint is applied to the foreign key in a one-to-one relationship?
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Which statement best describes a violation of a one-to-one relationship constraint?
Which statement best describes a violation of a one-to-one relationship constraint?
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To enforce one-to-one cardinality when a foreign key is placed in only one of the related tables, what action should be taken?
To enforce one-to-one cardinality when a foreign key is placed in only one of the related tables, what action should be taken?
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If a relationship between Person and SSN violates one-to-one relationship constraints, what could be a possible reason?
If a relationship between Person and SSN violates one-to-one relationship constraints, what could be a possible reason?
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Why might a foreign key appear in only one of the tables in a one-to-one relationship?
Why might a foreign key appear in only one of the tables in a one-to-one relationship?
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What is the consequence of a foreign key being nullable in a one-to-one relationship?
What is the consequence of a foreign key being nullable in a one-to-one relationship?
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What is a typical outcome of merging two entity sets that share a primary key?
What is a typical outcome of merging two entity sets that share a primary key?
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In a one-to-many relationship, which of the following constraints is generally applied to the foreign key?
In a one-to-many relationship, which of the following constraints is generally applied to the foreign key?
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What is often introduced in a many-to-many relationship to manage the association?
What is often introduced in a many-to-many relationship to manage the association?
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If a shared attribute is moved to a separate entity, the process exemplifies which concept?
If a shared attribute is moved to a separate entity, the process exemplifies which concept?
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What is the main purpose of a foreign key relationship in the relational model?
What is the main purpose of a foreign key relationship in the relational model?
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Why do weak entity sets exist if they can be converted into strong entities?
Why do weak entity sets exist if they can be converted into strong entities?
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Which design change is most appropriate for two entity sets that have a one-to-one relationship?
Which design change is most appropriate for two entity sets that have a one-to-one relationship?
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What happens when attributes are moved to a separate entity set?
What happens when attributes are moved to a separate entity set?
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Study Notes
Weak Entity Sets in Relational Databases
- Weak entity sets are used when entities lack their own unique identifier, relying upon a separate identifying entity for existence and identification.
- The identifying entity's primary key is crucial for deriving a primary key for the weak entity set.
- Weak entity relationships are often represented by partial keys which is a combination of the identifying entity's primary key and a unique attribute within the weak entity set.
- The presence of weak entity set implies a strong relationship between the entities.
- Weak entity sets signify a fundamental design principle for relational databases for ensuring data integrity and promoting a clear structure of relationships.
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Description
This quiz covers the concept of weak entity sets in relational databases, detailing how they depend on identifying entities for their unique identification. It discusses the role of primary keys in weak entities and emphasizes their importance in maintaining data integrity and structure within relational designs.
