10 Questions
What is the 'supervises' relationship between employees modeling?
It models the same entity set (employee) participating in the relationship set 'supervises' twice, once as the supervisor and once as the supervised employee.
What are the labels 'course_id' and 'prereq_id' called?
They are called roles.
How is the situation where one course is a prerequisite for another course depicted in the relationship set 'prereq'?
It is modeled by ordered pairs of course entities, where the first course takes the role of courseC1 and the second takes the role of prerequisite course C2.
What is the purpose of a top-down design process in entity-relationship modeling?
To designate sub-groupings within an entity set that are distinctive from other entities in the set.
How is specialization depicted in an entity-relationship model?
By a triangle component labeled ISA.
What is attribute inheritance in the context of entity-relationship modeling?
A lower-level entity set inherits all the attributes and relationship participation of the higher-level entity set to which it is linked.
What does the completeness constraint specify in the context of entity sets?
Whether an entity in the higher-level entity set must belong to at least one of the lower-level entity sets within a generalization.
How is total generalization specified in an ER diagram?
By adding the keyword total in the diagram and drawing a dashed line from the keyword to the corresponding hollow arrow-head to which it applies.
What is the default type of generalization in the context of completeness constraint?
Partial generalization.
What does it mean when the completeness constraint for a generalized higher-level entity set is total?
All entities in the higher-level entity set must belong to the lower-level entity sets.
Test your understanding of relationship sets in database systems with this quiz. Explore the concept of entities playing different roles in a relationship and the representation of 'supervises' relationship between employees.
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