Which of the following statements is correct with respect to entity integrity?a)Entity integrity constraints specify that primary key values can be composite. .b)Entity, integrity constraints are specified on individual relations.c)Entity integrity constraints are specified between weak entities.d)When entity integrity rules are enforced, a tuple in one relation that refers to another relation must refer to an existing tuple.Correct answer is option 'B'. Can you explain this answer?

Question

Answer

Introduction:
Entity integrity is a fundamental concept in database design that ensures the uniqueness and existence of primary key values within a relation. It helps maintain the consistency and integrity of the database by enforcing rules on the primary key values.

Explanation:
The correct statement with respect to entity integrity is option 'B' - Entity integrity constraints are specified on individual relations.

Entity Integrity Constraints:
Entity integrity constraints are rules that specify the conditions under which primary key values can exist or be modified within a relation. These constraints are typically specified at the time of creating the relation and are meant to enforce the uniqueness and existence of primary key values.

Individual Relations:
The statement in option 'B' is correct because entity integrity constraints are specified on individual relations. In other words, these constraints are defined at the level of each relation in the database schema.

Relation-level Constraints:
Entity integrity constraints are not specified between weak entities, as mentioned in option 'C'. Weak entities are entities that depend on another entity for their existence and do not have a unique identifier of their own.

Composite Primary Key:
Option 'A' is incorrect because entity integrity constraints do not specify that primary key values can be composite. A composite primary key is a primary key that consists of multiple attributes, but entity integrity constraints do not enforce or specify the use of composite primary keys.

Referential Integrity:
Option 'D' is incorrect because the statement refers to referential integrity, not entity integrity. Referential integrity constraints ensure that a foreign key value in one relation must refer to an existing primary key value in another relation.

Conclusion:
In conclusion, the correct statement with respect to entity integrity is option 'B'. Entity integrity constraints are specified on individual relations and ensure the uniqueness and existence of primary key values within those relations. They do not specify composite primary keys or enforce referential integrity.

Answer

Integrity constraint primary key contain unique and not null values.. so, it specify on individual relations

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