IT 214 Quiz 2

Entity

A 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.

Table

A _______ is perceived as a two-dimensional structure composed of rows and columns.

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.

Relational Schema

A textual representation for he database tables where each table is listed by is name followed by the list of its attributes.

Natural

A(n) _________ join links tables by selections only the rows with common values in their common attribute(s).

Equijoin

A(n) _________links tables on the basis of an equality condition that compares specified columns of each table.

False

All RDBMSs enforce integrity rules automatically.

Key attribute

Any attribute that is part of a key is known as a___________.

True

As far as 1:1 relationships should be, certain conditions absolutely required their use.

False

Because the relational modes uses attribute values to establish relationships among tables, many database users correctly assume that the term relations refers to such relationships.

False

Character data can contain any character or symbol intedended for mathematical manipulation.

False

Character data can contains any character or symbol intended for mathematical manipulation.

Logical Data Independence

Codd's rule of _________ states: 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.

True

Depending on the sophistication of the applications development software, nulls can create problems when functions such a as COUNT, AVERAGE, and SUM are used.

Many-to-many

Fortunately, the problems inherent in the ________ relationship can easily be avoided by creating a composite entity.

Referential

If the foreign hey contains either matching values or nulls, the table that makes use of that foreign key is said to exhibit _________ integrity.

Referential

If the the foreign key contains either matching valued or ills, the table that makes use of that foreign key is said to exhibit _______ integrity.

Synonym

In a database context, a(n) ________ indicates the use of different names to describe the same attribute.

Keys

In the relational model, these are important because they are sued to ensure that each row in a tables is uniquely idntifiable.

Null

No data entry at all is know as a(n) _________.

False

Only a single attribute, not multiple attributes, can define functional dependence.

Integrity

Referential ______ means that if the foreign key contains a value, that value refers to a existing valid tuple ( ros) in another relation.

False

Referential and entity integrity are two names for the same thing

Primary

Since it is used to long the tables that originally were relations in a M:N relationship, the composite entity structure includes-as foreign keys- at least the _______ keys of the tables that are to be linked.

True

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

True

The DIFFERENCE operation subtracts one table from the other.

NOT NULL

The _______ constraint can be placed on a column to ensure that every row int the table has a value for that column.

1:1

The _______ relationship should be rare in any relational database design.

System

The ________ catalog can be described as a detailed system data dictionary that describes al objects within the database, including data about table names, the table's creator and creations date, the number of columns in each table, the data type corresponding to each column, index file names, index creators, authorized users and access privileges.

Functionally dependent on

The attribute B is __________ the attribute A if each value in column A determines on and only one value in column B.

Entity

The following example exhibits _______ integrity: The CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column had no null entries, and all entries ar unique. Similarly, the AGENT table's primary key is AGENT_CODE, and this primary key column also is free of null entries.

Composite

The index key can have multiple attributes, this called a(n) ____________ index.

Relation

The logical vies of the realtionaldatabase is facilitated b the creation of data relationships based on a logical construct knows as a(n) ___________.

Relation

The logical vies of the relational database is facilitated bu the creations of data relationships based on a logical construct know as this.

False

The one-to-many relationship is easily implemented in the relational model by putting the foreign key of the "1" since int the table of the "many"side as a primary key.

False

The order of rows and columns is important to the DBMS.

False

The order of the rows and columns is important to the dbms.

Foreign

The proper use of _______ keys is crucial to controlling data redundancy.

Closure

The relational operators have the property of ___________: that is, the use of relational algebra operators on existing relations (tables) produces new relations.

Closure

The use of relational algebra operators on exiting relations (tables) produces new relations

False

There is never a good reason to use null values in a database.

Data Dictionary

This contains at least all of the arrticure names and characteristics for each table in the system.

Flags

To avoid nulls, some designers use special codes, know as ___________, to indicate the absence of some value.

Unique

When you define a table's primary key, the DBMS automatically creates a(n) _______ index on the primary key column(s) you declared.

PROJECT

Yields a vertical subset of a table

INTERSECT

Yields onlt the rows that appear in both tables

Logical

______ data can have only a true or false (yes or no) values.

SELECT

_______, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.

UNION

_________ combines all rows from two tables, excluding duplicate rows.

Outer

__________ joinsare especially useful when you are trying to determine what values in related tables cause referential integrity problems.

Predicate

________logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.

PROJECT

______yeilds a vertical subset of a table.