Lis 2780 Quiz 2

25 July 2022
4.7 (114 reviews)
88 test answers

Unlock all answers in this set

Unlock answers (84)
question
A table can be deleted from the database by using the ____ command.
answer
DROP TABLE
question
A(n) ____ is a query that is embedded (or nested) inside another query.
answer
Subquery
question
A(n) ____ is an alternate name given to a column or table in any SQL statemen
answer
Alias
question
SQL character data format(s) is(are) ____.
answer
CHAR and VARCHAR
question
Some RDBMSs, such as Oracle, automatically ____ data changes when issuing data definition commands.
answer
COMMIT
question
The SQL aggregate function that gives the average for the specific column is ____.
answer
AVG
question
The SQL aggregate function that gives the number of rows containing non-null values for the given column is ____.
answer
COUNT
question
The SQL aggregate function that gives the total of all values for a selected attribute in a given column is ____.
answer
SUM
question
The SQL command that lets you insert rows into a table is ____.
answer
INSERT
question
The SQL command that lets you permanently save data changes is ____.
answer
COMMIT
question
The SQL command that lets you select attributes from rows in one or more tables is ____.
answer
SELECT
question
The SQL command that modifies an attribute's values in one or more table's rows is ____.
answer
UPDATE
question
The ____ command is used to restore the table's contents to their previous values.
answer
ROLLBACK;
question
The ____ command is used with the ALTER TABLE command to modify the table by deleting a column.
answer
DROP
question
The ____ special operator is used to check whether an attribute value is null.
answer
IS NULL
question
The special operator used to check for similar character strings is ____.
answer
LIKE
question
The special operator used to check whether a subquery returns any rows is ____.
answer
EXISTS
question
The special operator used to check whether an attribute value is within a range of values is ____.
answer
BETWEEN
question
To delete a row from the PRODUCT table, use the ____ command.
answer
DELETE
question
When you issue the DELETE FROM tablename command without specifying a WHERE condition, ____.
answer
All Rows Will Be Deleted
question
existent independent
answer
one that can exist with out relating to any other entity
question
weak relationship
answer
dashed line two criteria: °must be existence dependent °the primary must contian part of the primary key of the parent entity
question
unary
answer
a relationship maintained between a single entity
question
Binary
answer
A relationship maintained by two entities
question
Ternary
answer
a relationship maintained by more than two entities
question
composite identifier
answer
it is an identifier is a key that is made up of more than one attribute
question
composite attribute
answer
one that can be broken down
question
recursive
answer
when tables have a relationship with themselves
question
associative entity
answer
•to break up a m:n relationship •resolving entity
question
derived attribute
answer
age
question
inheritance
answer
the subtype inherits the primary key of the super type
question
disjoint
answer
non overlapping
question
denormalization yields better______
answer
performance
question
prime key
answer
an attribute that is part of a key
question
data redundancy can reveal data _____
answer
integrity problems
question
partial dependency
answer
A partial dependency exists when a nonprime attribute is dependent on only a portion of the primary key.
question
atomic attribute
answer
cannot be further sub divided
question
A table can be removed (structure and data) from the database by using the ____ command.
answer
DROP TABLE
question
A relational table must not contain a(n) ____.
answer
repeating group
question
A table with a composite key, has all key attributes defined, has no repeating groups, and all its attributes are dependent on at least part of the primary key, is said to be in ____. Correct!
answer
1NF
question
A table that is in 1NF and includes no partial dependencies is said to be in ____.
answer
2NF
question
A table that is in 2NF and contains no transitive dependencies is said to be in ____.
answer
3NF
question
When designing a database, you should ____.
answer
make sure entities are in normal form before table structures are created
question
The most likely data type for a surrogate key is ____.
answer
Numeric
question
From a strictly database point of view, ____ attribute values can be calculated when they are needed to write reports or invoices.
answer
derived
question
For most business transactional databases, we should normalize relations into ____.
answer
3NF
question
The "____" characteristic of a primary key states that: The PK must uniquely identify each entity instance. A primary key must be able to guarantee unique values. It cannot contain nulls.
answer
unique values
question
The "____" characteristic of a primary key states that: The selected primary key must not be composed of any attribute(s) that might be considered a security risk or violation. For example, using a Social Security number as a PK in an EMPLOYEE table is not a good idea.
answer
security compliant
question
____ data refer to data whose values change over time and for which you must keep a history of the data changes.
answer
Time-variant
question
A ____ occurs when you have one entity in two 1:M relationships to other entities, thus producing an association among the other entities that *may* not be expressed in the model.
answer
fan trap
question
____ relationships occur when there are multiple (unnecessary) relationship paths between related entities.
answer
redundant
question
Normalization is
answer
the process for evaluating and correcting table structures to minimize data redundancies. the process for evaluating and correcting table structures to reduce the likelihood of data anomalies.
question
A table is in BCNF when
answer
every determinant in the table is a candidate key.
question
place the attributes that create the transitive dependency in a separate table.
answer
place the attributes that create the transitive dependency in a separate table. Make sure that the new table's primary key attribute is the foreign key in the original table.
question
Why is a table whose primary key consists of a single attribute automatically in 2NF when it is in 1NF?
answer
A dependency based on only a part of a composite primary key is called a partial dependency. Therefore, if the PK is a single attribute, there can be no partial dependencies.
question
An entity supertype
answer
is a generic entity type that is related to one or more entity subtypes contains the common characters
question
The entity subtype will store the data that is
answer
unique to the subtype
question
A specialization hierarchy depicts the
answer
arrangement of higher-level entity supertypes and lower-level entity subtypes
question
each entity instance of the supertype may appear in more than one subtype
answer
Overlapping subtypes
question
Partial completeness means
answer
not every supertype occurrence is a member of a subtype
question
Is it possible for a book to appear in the BOOK table without appearing in the PRODUCT table? Why or why not, explain?
answer
No. Subtypes can only exist within the context of a supertype.
question
An entity cluster
answer
is a "virtual" entity type used to represent multiple entities and relationships in the ERD. is formed by combining multiple interrelated entities into a single abstract entity object.
question
subtype discriminator
answer
is the attribute in the supertype entity that is used to determine to which entity subtype the supertype occurrence is related
question
A _____ attribute can be further subdivided to yield additional attributes.
answer
composite
question
A _____ attribute is one that cannot be subdivided.
answer
simple
question
A _____ entity has a primary key that is partially or totally derived from the parent entity in the relationship
answer
strong
question
A relationship is an association between _____
answer
entities
question
An entity is said to be _____-dependent if it can exist in the database only when it is associated with another related entity occurrence.
answer
existence
question
Ideally, an entity identifier is composed of _____ attribute(s).
answer
one
question
Ideally, an entity identifier is composed of _____ attribute(s).
answer
optional to
question
if an entity can exist apart from all of its related entities, then it is existence-independent, and it is referred to as a(n) _____ entity.
answer
strong
question
The decision to store _____ attributes in database tables depends on the processing requirements and the constraints placed on a particular application.
answer
derived
question
The existence of a(n) _____ entity indicates that its minimum cardinality is zero
answer
optional
question
The first step in building an entity-relationship diagram (ERD) is _____.
answer
identifying the attributes and primary keys that adequately describe the entities
question
_____ expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
answer
Cardinality
question
What two conditions must be met before an entity can be classified as a weak entity
answer
The entity must be existence-dependent on its parent entity. The entity must inherit at least part of its primary key from its parent entity.
question
What is a composite (bridge, join, link, associative) entity, and when is it used
answer
A composite entity is generally used to transform M:N relationships into 1:M relationships.
question
What is a recursive relationship? Given an example.
answer
when an entity is related to itself. For example, a COURSE may be a prerequisite to a COURSE.
question
total completeness
answer
a condition in which every supertype occurrence must be a member of at least one subtype
question
determinant
answer
an attribute specific row whose value directly determines other values in that row
question
denormalization
answer
a process by which a table is changed from a higher level normal form to a lowerlevel normal form
question
natural identifier
answer
a generally accepted identifier for real world objects.
question
candidate key
answer
a key that does not contain a subset of attributes that is itself a superkey
question
composite key
answer
a multi-valued key
question
an attribute that is not part of a key
answer
non-prime attribute
question
connectivity
answer
types of relationships between entities
question
generalization
answer
the grouping of common attributes into a supertype entity
question
specialization
answer
the grouping of unique attributes into a subtype entity