Which of the following statements is/are TRUE? (i) A weak entity set is identified solely by its partial key (discriminator). (ii) The identifying relationship type between a weak entity type and its owner entity type must have total participation from the weak entity type.
Only (ii)
Analyzing Weak Entity Set Identification and Participation
This section analyzes the truthfulness of the two statements regarding weak entity sets in database design.
Statement (i): Weak Entity Identification
Statement (i) claims that a weak entity set is identified solely by its partial key (discriminator). This is incorrect.
- A weak entity set depends on an owner entity set for its identification.
- While the partial key (discriminator) uniquely identifies weak entities within a specific owner entity, the complete identification requires both the partial key and the primary key of the associated owner entity.
- Without the owner's key, the partial key alone cannot guarantee uniqueness across the entire database.
Statement (ii): Identifying Relationship Participation
Statement (ii) states that the identifying relationship type between a weak entity type and its owner entity type must have total participation from the weak entity type. This is correct.
- By definition, a weak entity cannot exist independently of its owner entity.
- Every instance of a weak entity must be associated with at least one instance of its owner entity through the identifying relationship.
- This mandatory association signifies total participation. If the owner is removed, the weak entity must also be removed.
Conclusion on Statements
Based on the analysis:
- Statement (i) is FALSE.
- Statement (ii) is TRUE.
Therefore, the only true statement is (ii).
Final Answer Selection
The option that correctly identifies only statement (ii) as true is the correct choice.
The correct option is: Only (ii).
Important Questions from ER Model
______ are some problems that can occur when creating an entity-relationship model.
Relations produced from E - R Model will always be in ______
Consider the following statements:
Statement I: Composite attributes cannot be divided into smaller subparts.
Statement II: Complex attribute is formed by nesting composite attributes and multi- valued attributes in an arbitrary way.
Statement III: A derived attribute is an attribute whose values are computed from other attribute.
Which of the following is correct?
A company is consuming parts in the manufacturing of other products. Each of the part is either manufactured within the company or purchased from the external suppliers or both. For each part, partnumber, partname is maintained. Attribute batchnumber is maintained if the consumed part is manufactured in the company. If part is purchased from external supplier, then supplier name is maintained. Which of the following constraints need to be considered when modelling class/subclass concepts in ERD for the given problem.
Which of the following key constraints is required for functioning of foreign key in the context of relational database?
