Oracle Chapter 7 + 8

A single relationship can be both Recursive and Hierarchal at the same time True False

False

All relationships participating in an arc must be mandatory. True False

False

Arcs model an Exclusive OR constraint. True False

True

To visually represent exclusivity between two or more relationships in an ERD you would most likely use an ________. a. Arc b. Relationship c. UID d. Attribute

a

When a relationship may or may not be transferable, depending on time, this is know as a/an: a. Conditional Non-transferable Relationship b. Non-transferable Relationship. c. Arc. d. Transferable Relationship

a

Which of the following would be a logical constraint when modeling time for a City entity? a. Cites may change their names and/or country association if the borders of a country change. b. People are born in the city and people die in the city. c. If you are doing a system for any French City, you would need security clearance. d. Daily traffic patterns must be monitored to determine how many law enforcement officers are needed.

a

Which of the following would be a logical constraint when modeling time for a country entity? a. Countries may change their names and/or borders over a period of time. b. Daily traffic patterns must be monitored to determine which countries are overcrowded. c. If you are doing a system for France or Germany, you would need security clearance. d. People have births and deaths in their countries that must be tracked by the system.

a

Which of the following would be a logical constraint when modeling time for a country entity? a. Countries may change their names and/or borders over a period of time. b. Daily traffic patterns must be monitored to determine which countries are overcrowded. c. If you are doing a system for France or Germany, you would need security clearance. d. People have births and deaths in their countries that must be tracked by the system.

a

Why would you want to model a time component when designing a system that lets people buy bars of gold? a. The price of gold fluctuates and, to determine the current price, you need to know the time of purchase. b. You would not want to model this; it is not important. c. Sales people must determine where the gold is coming from. d. The Government of your country might want to be notified of this transaction.

a

Which of the following scenarios should be modeled so that historical data is kept? (Choose two) a. LIBRARY and BOOK= b. LIBRARY and NUMBER OF BOOKS c. STUDENT and AGE d. STUDENT and GRADE

a, d

Which of the following statements are true to enhance the readability of ERDs? (Choose Two) a. Relationship lines should not cross b. Crossing relationship lines help the readability of the diagram. c. Crows feet (the many-ends of relationships) should consistently point the same direction where possible, either South & East or North & West d. It does not matter which way the crows feet (many ends of a relationship) point.

a,c

Which of the following scenarios should be modeled so that historical data is kept? (Choose two) a. CUSTOMER and ORDERS b. TEACHER and AGE c. BABY and AGE d. CUSTOMER and PAYMENTS

a,d

A relationship between an entity and itself is called a/an: a. General Relationship b. Recursive Relationship c. Invalid Relationship d. Hierarchical Relationship

b

Arcs are used to visually represent _________ between two or more relationships in an ERD. a. Differences b. Exclusivity c. Sameness d. Inheritance

b

Cascading UIDs are a feature often found in what type of Relationship? a. Invalid Relationship b. Hierarchical Relationship c. General Relationship d. Recursive Relationship

b

Which of the following is a logical constraint that could result from considering how time impacts an example of data storage? a. End Date must be before the Start Date. b. An ASSIGNMENT may only refer to an EMPLOYEE with a valid employee record at the Start Date of the ASSIGNMENT. c. Dates must be stored with Time. d. EMPLOYEE periods can overlap causing the database to crash.

b

Which of the following statements are true for ERD's to enhance their readability. (Choose Two) a. You must ensure that you have every single entity--even if hundreds of them exist--on one single, big diagram. b. It is OK to break down a large ERD into subsets of the overall picture. By doing so, you end up with more than one ERD that, taken together, documents the entire system. c. The crows feet (many ends) can point whichever way is the easiest to draw. d. Avoid crossing one relationship line with another.

b, d

A Recursive Relationship is represented on an ERD by a/an: a. Dog's Tail b. Crow's Foot c. Pig's Ear d. Single Toe

c

Every business has restrictions on which attribute values and which relationships are allowed. These are known as: a. Attributes b. Entities c. Constraints d. Relationships

c

Which of the following would be best represented by an arc? a. STUDENT (senior, male) b. STUDENT (Grade A student, Average Student) c. STUDENT ( University, Technical College) d. STUDENT (graduating, female)

c

Which of the following would best be represented by an arc? a. STUDENT (Grade A student, Average Student) b. TEACHER (Female, Bob) c. DELIVERY ADDRESS (Home, Office) d. PARENT (Girl, Bob)

c

If you have an entity with a DATE attribute, in addition to other attributes that track date characteristics, you should create a DAY entity. true false

true

In a payroll system, it is desirable to have an entity called DAY with a holiday attribute when you want to track special holiday dates. true false

true

In an ERD, it is a good idea to group your entities according to the expected volumes. By grouping high volume entities together, the diagrams could become easier to read. true false

true

Modeling historical data is optional. true false

true

No formal rules exist for drawing ERD's. The most important thing is to make sure that all entities, attributes, and relationships are documented on the diagram, and the diagram is clear and readable. true false

true

You are doing a data model for a computer sales company where the price of postage depends upon the day of the week that goods are shipped. So shipping is more expensive if the customer wants a delivery to take place on a Saturday or Sunday. What would be the best way to model this? a. Allow them to enter whatever delivery charge they want. b. Email current prices to all employees whenever a price changes. c. Use a Delivery Day entity, which holds prices against week days, and ensure the we also have an attribute for the Requested Delivery Day in the Order Entity. d. Update the prices in the system, print out the current prices when they change, and pin them on the company noticeboard.

c

How do you know when to use the different types of time in your design? a. The rules are fixed and should be followed. b. Always model time; you can take it out later if it is not needed. c. You would first determine the existence of the concept of time and map it against the Greenwich Mean Time. d. It depends on the functional needs of the system.

d

What is the function of logging or journaling in conceptual data models? a. Creates a fixed time for all events in a data model. b. Gives a timestamp to all entities. c. Represents entities as time in the data model. d. Allows you to track the history of attribute values, relationships, and/or entire entities.

d

Which of the following can be added to a relationship? a. An attribute b. A composite attribute c. An optional attribute can be created d. An arc can be assigned

d

You are doing a data model for a computer sales company where the price fluctuates on a regular basis. If you want to allow the company to modify the price and keep track of the changes, what is the best way to model this? a. A. Create a product entity and a related price entity with start and end dates, and then let the users enter the new price whenever required. b. B. Create a new item and a new price every day. c. C. Use a price entity with a start and end date d. D. Allow them to delete the item and enter a new one. e. E. Both A and C

e

A recursive relationship must be Mandatory at both ends. True False

false

All systems must have an entity called WEEK with a holiday attribute so that you know when to give employees a holiday. true false

false

All systems must include functionality to provide logging or journaling in conceptual data models. true false

false

Arcs are Mandatory in Data modeling. All ERD's must have at least one Arc. True False

false

Formal rules exist for drawing ERD's. You must always follow them, even if it results in an ERD that is difficult to read. true false

false

Historical data must never be kept. true false

false

Historical data should always be kept. true false

false

In an ERD, High Volume Entities usually have very few relationships to other entities. true false

false

There are no circumstances where you would create a DAY entity. true false

false

There is no point in trying to group your entities together on your diagram according to volume, and making a diagram look nice is a waste of time. true false

false

When modeling historical data the unique identifier is always made up of a barred relationship from the original two entities. true false

false

You must make sure all entities of a proposed system can fit onto one diagram. It is not allowed to break up a data model into more than one diagram. True False

false

A Hierarchical relationship is a series of relationships that reflect entities organized into successive levels. true false

true

A particular problem may be solved using either a Recursive Relationship or a Hierarchical Relationship, though not at the same time. True False

true

An arc can often be modeled as Supertype and Subtypes. True False

true

Business organizational charts are often modeled as a Hierarchical relationship. True False

true

Conditional non-transferability refers to a relationship that may or may not be transferable, depending on time. true false

true