Database Design Section 8

1.  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 or False?
Mark for Review (1) Point
True(*)
False
2.  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 or False?
Mark for Review (1) Point
True
False(*)
3.  In an ERD, High Volume Entities usually have very few relationships to other entities. True or False?

Mark for Review (1) Point
True
False(*)
4.  Which of the following statements are true for ERD's to enhance their readability. (Choose Two)

(Choose all correct answers)
Mark for Review (1) Point
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. (*)
Avoid crossing one relationship line with another. (*)
5.  Modeling historical data is optional. True or False?
Mark for Review (1) Point
True(*)
False
6.  When you add the concept of time to your data model, your model becomes more complex. True or False?
Mark for Review (1) Point
True(*)
False
7.  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 or False?
Mark for Review (1) Point
True(*)
False
8.  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 or False?
Mark for Review (1) Point
True(*)
False
9.  All systems must have an entity called WEEK with a holiday attribute so that you know when to give employees a holiday. True or False?
Mark for Review (1) Point
True
False(*)
10.  Modeling historical data can produce a unique identifier that includes a date. True or False?
Mark for Review (1) Point
True(*)
False
11.  Historical data should always be kept. True or False?
Mark for Review (1) Point
True
False(*)
12.  Which of the following scenarios should be modeled so that historical data is kept? (Choose two)

(Choose all correct answers)
Mark for Review (1) Point

CUSTOMER and PAYMENTS (*)

CUSTOMER and ORDERS (*)
13.  Why would you want to model a time component when designing a system that lets people buy bars of gold?
Mark for Review (1) Point
The price of gold fluctuates and, to determine the current price, you need to know the time of purchase. (*)
14.  When a system requires that old values for attributes are kept on record, this is know as Journaling or Logging. True or False?
Mark for Review (1) Point
True(*)
False
15.  All systems must include functionality to provide logging or journaling in conceptual data models. True or False?
Mark for Review (1) Point
True
False(*)