oracle sections 4,5 – Flashcards
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A subtype can have a relationship not shared by the supertype. True or False?
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True
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Which of the following is the best scenario for using supertype/subtype entities:
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A vehicle dealership that sells boats on trailers, cars, and trucks.
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All instances of a subtype must be an instance of the supertype. True or False?
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True
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All instances of the supertype are also instances of one of the subtypes. True or False?
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True
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If subtypes are listed, a supertype should have at least two subtypes. True or False?
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True
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Which of the following is a TRUE statement about the diagram below?
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Every A is a B
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Which of the following is true about supertypes and subtypes?
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Subtypes inherit the relationships and attributes of the supertype.
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The "Other" subtype is best used:
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As an extra subtype to ensure that the list of subtypes is exhaustive. By having an "Other" subtype, all instances of the Supertype will have a subtype to belong to.
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How should you handle constraints that cannot be modeled on an ER diagram?
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List them on a separate document to be handled programmatically
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How would you model a business rule that states that on a student's birthday, he does not have to attend his classes?
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You cannot model this. You need to document it
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Which of the following is an example of a structural business rule?
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All employees must belong to at least one department.
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'Only managers can approve travel requests' is an example of which of the following?
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A procedural business rule.
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A business rule such as "All accounts must be paid in full within 10 days of billing" is best enforced by:
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Hiring a programmer to create additional programming code to identify and report accounts past due.
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Business rules are important to data modelers because:
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They capture all of the needs, processes, and required functionality of the business.
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Why is it important to identify and document business rules?
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It allows you to create your data model and then check it for accuracy.
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If a relationship can be moved between instances of the entities it connects, it is said to be:
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Transferable
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A non-transferable relationship is represented by which of the following symbols?
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Diamond
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Non-transferable relationships can only be mandatory, not optional. True or False?
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False
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Which of the following are relationship types?
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Many to Many One to Many
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What uncommon relationship is described by the statements: "Each LINE must consist of many POINTS and each POINT must be a part of many LINES".
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Many to Many Mandatory
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When are relationships unnecessary?
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When you can derive the relationship from other relationships in the model
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If the same relationship is represented twice in an Entity Relationship Model, it is said to be:
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Redundant
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Which of the following pairs of entities is most likely to be modeled as a M:M relationship?
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STUDENT and CLASS RENTAL CAR and DRIVER
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If an intersection entity is formed that contains no attributes of its own, its uniqueness may be modeled by
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Barring the relationships to the original entities.
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Many-to-Many relationships are perfectly acceptable in a finished ERD. There is no need to do any more work on them. True or False?
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False
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When you resolve a M:M by creating an intersection entity, this new entity will always inherit:
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A relationship to each entity from the original M:M.
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Many to many relationships between entities usually hide what?
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Another entity
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When resolving a M:M relationship, the new relationships will always be __________ on the many side.
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Mandatory
