Chapter 3 The Relational Database Model
10.) The _____ relationship is the "relational model ideal."
1:M
18.) A video game store has a table with its users. What type of data type is best for the attribute of being an adult?
Logical
15.) On a table of students the attributes of student code, name, surname, gpa, birth date, and phone number. What data type is more appropriate for the gpa attribute?
Numeric
2.) Which of the following is a reason to use indices in a database?
Retrieve data ordered by a specific attribute.
20.) When using a foreign key the same value shows up in several rows. Why is this not considered data redundancy?
The elimination of the foreign key would result in losing the information of the relation.
5.) Consider the following table attribute 1 1 2 2 1 attribute 2 Alex Roxy Alex Tom attribute 3 132 132 254 132 attribute 4 AX RY AX TM Which of the following pairs of attributes could have a functional dependence?
attribute 2, attribute 4
9.) A _____ contains all of the attribute names and characteristics for each table in the system.
data dictionary
3.) The proper use of _____ keys is crucial to controlling data redundancy.
foreign
11.) Relations are a ________ construct, thus it's easier for users to think in terms of tables.
mathematical
4.) Relational algebra defines the theoretical way of manipulating table contents using _______..
relational operators
14.) Define entity integrity. What are the two requirements to ensure entity integrity?
Entity integrity is the condition in which each row (entity instance) in the table has its own unique identity. To ensure entity integrity, the primary key has two requirements: (1) all of the values in the primary key must be unique. (2) no key attribute in the primary key can contain a null.
12.) A table is a three dimensional structure composed of depth, width, and height.
False
19.) A primary key can't be null, but it can contain null attributes.
False
7.) The row's range of permissible values is known as its domain.
False
8.) Only a single attribute, not multiple attributes, can define functional dependence.
False
1.) When you define a table's primary key, the DBMS automatically creates a(n) _____ index on the primary key column(s) you declared.
unique
6.) What relational operation would give a table with the names in table1 that have at least one entry in table 2 with a total greater than 100?
REFER TO THE STUDY GUIDE, Correct. By doing a join with the SELECT of table2 it is guaranteed that only those with a total greater than 100 are included. Then the projection gives only the names.
13.) What kind of integrity is violated in the previous database?
REFER TO THE STUDY GUIDE, referential integrity Correct. The row with attribute1 = 2 in TABLE1 references an entity with attribute3 = 1 in TABLE2. But there is no such entity. That violates referential integrity.
16.) An index is composed of an index key and pointers. What is the function of the pointers?
Shows the location of the occurrences of a particular index value.
17.) A database stores the data of the sales using the primary key RECEIVE_NUM in the SALE table and the products in the PRODUCT table with primary key PROD_NUM. To create the relation that represents what products were sold in a SALE a M:N relationship is necessary. What should be used to represent this in a relational model?
composite entity with RECEIVE_NUM + PROD_NUM
