Chapter 3: Quiz

True

A data dictionary contains metadata-data about data. Select one: True False

True

A data dictionary is sometimes described as "the database designer's database" because it records the design decisions about tables and their structures. Select one: True False

False

A foreign key must exist in both tables that have a relationship. Select one: True False

True

A left outer join on tables CUSTOMER and AGENT yields all of the rows in the CUSTOMER table, including those that do not have a matching value in the AGENT table. Select one: True False

True

A null is created when you press the Enter key or the Tab key to move to the next entry without making a prior entry of any kind. Select one: True False

Bridge

Another name for a composite entity is a ______ entity. Select one: a. bridge b. linked c. directive d. referring

True

As rare as 1:1 relationships be, certain conditions absolutely require their use. Select one: True False

False

Because the relational model uses attribute values to establish relationships among tables, many database users correctly assume that the term relation refers to such relationships. Select one: True False

False

Character data can contain any character or symbol intended for mathematical manipulation. Select one: True False

True

Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used. Select one: True False

True

Each table in a relational database must have a primary key. Select one: True False

True

If the attribute (B) is functionally dependent on a composite key (A) but not on any subset of that composite key, the attribute (B) is fully functionally dependent on (A). Select one: True False

False

In a natural join, the column on which the join was made occurs twice in the new table. Select one: True False

False

In a relational model, if A determines B, C, and D, you write A = B, C, D. Select one: True False

False

Only a single attribute, not multiple attributes, an define functional dependence. Select one: True False

False

Referential and entity integrity are two names for the same thing. Select one: True False

True

Tables must have the same attribute characteristics (the columns and domains must be compatible) to be used in a UNION. Select one: True False

False

The SELECT operator yields a vertical subset of a table. Select one: True False

1:M

The ______ relational type is the "relational model ideal." Select one: a. 1:1 b. 1:M c. M:1 d. M:N

True

You can think of a table as a persistent representation of a logical relation. Select one: True False