Constraints
Question 1 |
Which of the following statements about “total specialization” constraint is TRUE?
Every entity in the subclass must be a member of the superclass. | |
Every entity in the superclass must be a member of at least one subclass in the specialization. | |
At least one entity in the superclass must be a member of at least one subclass in the specialization. | |
Every entity in the superclass must be a member of all subclass in the specialization. |
Question 1 Explanation:
→The total specialization rule demands that every entity in the superclass belong to some subclass.
→The partial specialization rule allows an entity to not belong to any of the subclasses
Question 2 |
Which of the following is used to specify whether the existence of an entity depends on its being related to another entity via the relationship type?
Entity integrity constraint | |
Foreign key constraint | |
Cardinality ratio | |
Participation constraint |
Question 3 |
Which of the following constraints enforces that the value of the primary key cannot be Null?
Key Constraint | |
Foreign key constraint | |
Entity integrity constraint | |
Domain constraint |
Question 3 Explanation:
The entity integrity constraint states that primary key value can't be null. This is because the primary key value is used to identify individual rows in relation and if the primary key has a null value, then we can't identify those rows.
Question 4 |
Integrity constraints ensure that changes made to the database by authorized users do not result into loss of data consistency. Which of the following statement(s) is (are) true w.r.t. the examples of integrity constraints ?
(A) An instructor Id. No. cannot be null, provided Instructor Id No. being primary key.
(B) No two citizens have same Adhar-Id.
(C) Budget of a company must be zero.
(A) An instructor Id. No. cannot be null, provided Instructor Id No. being primary key.
(B) No two citizens have same Adhar-Id.
(C) Budget of a company must be zero.
(A), (B) and (C) are true. | |
(A) false, (B) and (C) are true. | |
(A) and (B) are true; (C) false. | |
(A), (B) and (C) are false |
Question 4 Explanation:
Primary key, every table have at least one attribute as “primary key”. No primary key should ever have null values.
Statement-1: TRUE: Here, instructor ID is primary key. So, they mentioned it is not null.
Statement-2: TRUE: No two citizens have same Adhar-Id. It is clear example of primary key.
Statement-3: FALSE: Budget of a company must be zero. It is violated constraint of “not null”. Because entity integrity constraints should not accept not null but referential integrity constraints will accept null value.
Statement-1: TRUE: Here, instructor ID is primary key. So, they mentioned it is not null.
Statement-2: TRUE: No two citizens have same Adhar-Id. It is clear example of primary key.
Statement-3: FALSE: Budget of a company must be zero. It is violated constraint of “not null”. Because entity integrity constraints should not accept not null but referential integrity constraints will accept null value.
There are 4 questions to complete.