Multiple Choice Questions

The CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of _____ integrity.
  • False
  • closure
  • True
  • entity
The one-to-many (1:M) relationship is easily implemented in the relational model by putting the foreign key of the "1" side in the table of the "many" side as a primary key.
  • True
  • False
A primary key is a(n) _____ key chosen to be the primary means by which rows of a table are uniquely identified.
  • attribute
  • Cartesian
  • candidate
  • integrity
The _____ catalog can be described as a detailed system data dictionary that describes all objects within the database, including data about table names, the table's creator and creation date, the number of columns in each table, the data type corresponding to each column, index filenames, index creators, authorized users, and access privileges.
  • False
  • closure
  • system
  • system catalog
To be considered minimally relational, the DBMS must support the key relational operators _____, PROJECT, and JOIN.
  • synonym
  • SELECT
  • PROJECT
  • Julian
Referential _____ dictates that the foreign key must contain values that match the primary key in the related table, or must contain null.
  • integrity
  • candidate
  • True
  • foreign key
A _____ key is defined as a key that is used strictly for data retrieval purposes.
  • secondary
  • candidate
  • inner join
  • data dictionary
A(n) _____ only returns matched records from the tables that are being joined.
  • unique
  • inner join
  • index
  • quijoin
_____, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.
  • quijoin
  • relation
  • SELECT
  • candidate
Describe the use of null values in a database.
  • Null values are problematic in a relational model. A null is the absence of any data value, and it is never allowed in any part of the primary key. From a theoretical perspective, it can be argued that a table that contains a null is not properly a relational table at all. From a practical perspective, however, some nulls cannot be reasonably avoided. For example, not all students have a middle initial. As a general rule, nulls should be avoided as much as reasonably possible. In fact, an abundance of nulls is often a sign of a poor design. Also, nulls should be avoided in the database because their meaning is not always identifiable. For example, a null could represent:• An unknown attribute value.• A known, but missing, attribute value.• A "not applicable" condition.
  • INTERSECT yields only the rows that appear in both tables. As with UNION, the tables must be union-compatible to yield valid results. For example, you cannot use INTERSECT if one of the attributes is numeric and one is character-based. For the rows to be considered the same in both tables and appear in the result of the INTERSECT, the entire rows must be exact duplicates.
  • column
  • True
As rare as 1:1 relationships should be, certain conditions absolutely require their use.
  • True
  • False
To avoid nulls, some designers use special codes, known as _____, to indicate the absence of some value.
  • False
  • flags
  • keys
  • SELECT
The proper use of _____ keys is crucial to controlling data redundancy.
  • bridge
  • foreign key
  • PROJECT
  • foreign
When two or more tables share the same number of columns, and when their corresponding columns share the same or compatible domains, they are said to be _____.
  • union-compatible
  • unique
  • entity
  • integrity
Proper data _____ design requires carefully defined and controlled data redundancies to function properly.
  • Cartesian
  • foreign key
  • homonym
  • warehousing
The _____ constraint can be placed on a column to ensure that every row in the table has a value for that column.
  • inner join
  • foreign key
  • NOT NULL
  • data dictionary
_____ returns only the attributes requested, in the order in which they are requested.
  • Predicate
  • SELECT
  • PROJECT
  • foreign
The DIVIDE operation uses one single-column table (e.g., column "a") as the divisor and one two-column table (e.g., columns "a" and "b") as the dividend.
  • True
  • False
The _____ relationship is the "relational model ideal."
  • 1:1
  • 1:M
  • True
  • index
In a natural join, the column on which the join was made occurs twice in the new table.
  • True
  • False
One characteristic of generalization hierarchies is that they are implemented as _____ relationships.
  • SELECT
  • True
  • 1:1
  • keys
The DIFFERENCE operator subtracts one table from the other.
  • True
  • False
_____ is the real power behind the relational database, allowing the use of independent tables linked by common attributes
  • JOIN
  • foreign key
  • Julian
  • quijoin
PRODUCT yields all possible pairs of rows from two tables, also known as the _____ product.
  • integrity
  • Cartesian
  • candidate
  • attribute
In a relational table, each column has a specific range of values known as the _____ domain.
  • attribute
  • candidate
  • attibutes
  • closure
In a database context, the word _____ indicates the use of the same attribute name to label different attributes.
  • homonym
  • keys
  • SELECT
  • synonym
Another name for a composite entity is a(n) _____ entity.
  • superkey
  • bridge
  • False
  • True
Character data can contain any character or symbol intended for mathematical manipulation.
  • True
  • False
You can think of a table as a persistent representation of a logical relation.
  • True
  • False
Define entity integrity. What are the two requirements to ensure entity integrity?
  • attibutes
  • False
  • index
  • 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.
The _____ relationship is the relational database norm.
  • index
  • 1:1
  • M:N
  • 1:M
The order of the rows and columns is important to the DBMS.
  • True
  • False
Describe the use of the INTERSECT operator.
  • True
  • 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.
  • INTERSECT yields only the rows that appear in both tables. As with UNION, the tables must be union-compatible to yield valid results. For example, you cannot use INTERSECT if one of the attributes is numeric and one is character-based. For the rows to be considered the same in both tables and appear in the result of the INTERSECT, the entire rows must be exact duplicates.
  • superkey
According to Codd's _____ rule of relational databases, application programs and ad hoc facilities are logically unaffected when changes are made to the table structures that preserve the original table values (changing order of columns or inserting columns).
  • union-compatible
  • Predicate
  • guaranteed Access
  • logical data independence
A(n) _____ is an orderly arrangement used to logically access rows in a table.
  • unique
  • True
  • inner join
  • index
RDBMSs enforce integrity rules automatically.
  • True
  • False
A _____ key can be described as a minimal superkey, a superkey without any unnecessary attributes.
  • candidate
  • natural
  • attibutes
  • Predicate
A _____ contains at least all of the attribute names and characteristics for each table in the system.
  • candidate
  • quijoin
  • NOT NULL
  • data dictionary
Each table in a relational database must have a primary key.
  • True
  • False
A(n) _____ links tables on the basis of an equality condition that compares specified columns of each table.
  • natural
  • inner join
  • quijoin
  • data dictionary
The _____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents.
  • Outer joins
  • NOT NULL
  • foreign key
  • system catalog
According to Codd's _____ rule of relational databases, if the system supports low-level access to the data, users must not be allowed to bypass the integrity rules of the database.
  • False
  • logical data independence
  • Outer joins
  • non-subversion
T/F The practical significance of taking the logical view of a database is that it serves as a reminder of the simple file concept of data storage.
  • True
  • False
When you define a table's primary key, the DBMS automatically creates a(n) _____ index on the primary key column(s) you declared.
  • Julian
  • True
  • union-compatible
  • unique
An index key can have multiple _____ (a composite index).
  • superkey
  • attibutes
  • secondary
  • candidate
If one department chair—a professor—can chair only one department, and one department can have only one department chair. The entities PROFESSOR and DEPARTMENT exhibit a(n) _____ relationship.
  • homonym
  • 1:1
  • True
  • keys
Define an index. Explain the role of indexes in a relational database.
  • unique
  • False
  • Null values are problematic in a relational model. A null is the absence of any data value, and it is never allowed in any part of the primary key. From a theoretical perspective, it can be argued that a table that contains a null is not properly a relational table at all. From a practical perspective, however, some nulls cannot be reasonably avoided. For example, not all students have a middle initial. As a general rule, nulls should be avoided as much as reasonably possible. In fact, an abundance of nulls is often a sign of a poor design. Also, nulls should be avoided in the database because their meaning is not always identifiable. For example, a null could represent:• An unknown attribute value.• A known, but missing, attribute value.• A "not applicable" condition.
  • An index is an orderly arrangement used to logically access rows in a table. From a conceptual point of view, an index is composed of an index key and a set of pointers. The index key is, in effect, the index's reference point. More formally, an index is an ordered arrangement of keys and pointers. Each key points to the location of the data identified by the key. DBMSs use indexes for many different purposes. An index can be used to retrieve data more efficiently. Indexes can also be used by a DBMS to retrieve data ordered by a specific attribute or attributes. For example, creating an index on a customer's last name will allow you to retrieve the customer data alphabetically by the customer's last name. Also, an index key can be composed of one or more attributes. Indexes play an important role in DBMSs for the implementation of primary keys. When you define a table's primary key, the DBMS automatically creates a unique index on the primary key column(s) you declared
In a relational model, _____ are used to establish relationships among tables and to ensure the integrity of the data
  • keys
  • attribute
  • False
  • closure
Only a single attribute, not multiple attributes, can define functional dependence.
  • True
  • False
Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used.
  • True
  • False
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.
  • True
  • False
The idea of determination is unique to the database environment.
  • True
  • False
A(n) ______ provides a detailed description of all tables found within the user/designer-created database.
  • quijoin
  • natural
  • candidate
  • data dictionary
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Multiple Choice Questions
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