Question 1

The response of the DBMS to a query is the ____.

Accepted Answer

query result set

Question 2

Constraints

Accepted Answer

- are important because they help to ensure data integrity.  - is a restriction placed on the data.

Question 3

Primary Key

Accepted Answer

- used to ensure that each row in a table is uniquely identifiable  - used to uniquely identify each entity instance.

Question 4

The Crow\'s foot symbol with two parallel lines indicates ____ cardinality.

Accepted Answer

(1,1)

Question 5

Partial completeness is symbolized by ____.

Accepted Answer

a circle over a single line

Question 6

An entity cluster is formed by combining multiple interrelated entities into ____.

Accepted Answer

a single abstract entity object

Question 7

If one exists (and there are no security issues), a data modeler may use a ____ as the primary key of the entity being modeled.

Accepted Answer

natural identifier

Question 8

Within a specialization hierarchy, every subtype can have ____ supertype(s) to which it is directly related.

Accepted Answer

only one

Question 9

____ is a generic entity type that is related to one or more entity subtypes.

Accepted Answer

an entity supertype

Question 10

specialization hierarchy

Accepted Answer

depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities).

Question 11

One important inheritance characteristic is that all entity subtypes inherit their ____ key attribute from their supertype.

Accepted Answer

primary

Question 12

Redundant relationships

Accepted Answer

occur when there are multiple (unnecessary) relationship paths between related entities.

Question 13

time-variant data

Accepted Answer

data whose values change over time and for which you must keep a history of the data changes.  - requires a multivalued attribute which is resolved by creating a new table.

Question 14

fan trap

Accepted Answer

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.

Question 15

For most business transactional databases, we should normalize relations into ____.

Accepted Answer

3NF

Question 16

When designing a database, you should ____.

Accepted Answer

make sure entities are in normal form before table structures are created

Question 17

From a strictly database point of view, ____ attribute values can be calculated when they are needed to write reports or invoices.

Accepted Answer

derived

Question 18

The most likely data type for a surrogate key is ____.

Accepted Answer

numeric

Question 19

Data redundancy produces ____.

Accepted Answer

data integrity problems

Question 20

A relational table must not contain a(n) ____.

Accepted Answer

repeating group

Question 21

A table that is in 2NF and contains no transitive dependencies is said to be in ____.

Accepted Answer

3NF

Question 22

An atomic attribute ____.

Accepted Answer

cannot be further subdivided

Question 23

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 ____.

Accepted Answer

1NF

Question 24

A table that is in 1NF and includes no partial dependencies is said to be in ____.

Accepted Answer

2NF

Question 25

SQL character data format(s) is(are) ____.

Accepted Answer

CHAR and VARCHAR

Question 26

The SQL command that modifies an attribute\'s values in one or more table\'s rows is ____.

Accepted Answer

UPDATE

Question 27

The SQL command that lets you insert rows into a table is ____.

Accepted Answer

INSERT

Question 28

To list all the contents of the PRODUCT table, you would use ____.

Accepted Answer

SELECT * FROM PRODUCT;

Question 29

The SQL command that lets you select attributes from rows in one or more tables is ____.

Accepted Answer

SELECT

Question 30

What is a relationship, and what three types of relationships exist?

Accepted Answer

A relationship is an association among (two or more) entities.   Three types of relationships exist: one-to-one (1:1), one-to-many (1:M), and many-to-many (M:N or M:M.)

Question 31

Primary Key (ENTITY INTEGRITY)

Accepted Answer

Entity integrity describes a condition in which all tuples (i.e., rows or records) within a table are uniquely identified by their primary key. The unique value requirement prohibits a null primary key value, because nulls are not unique.  - ensures that each row is uniquely identified by the primary key.

Question 32

Foreign Key (REFERENTIAL INTEGRITY)

Accepted Answer

Referential integrity describes a condition in which a foreign key value has a match in the corresponding table, or in which the foreign key value may be null (depending upon the business rules).  - means that, if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.

Question 33

What are the requirements that two relations must satisfy in order to be considered union-compatible?

Accepted Answer

Both must have the same number of attributes (columns) and corresponding attributes (columns) must have the same (or compatible) domains (data types).

Question 34

Weak Entity

Accepted 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 35

Strong Relationship

Accepted Answer

- requires weak or existent-dependent entities that have primary keys partially or fully made up of the parent entity\'s primary key.   - In a Crow\'s Foot ERD, a strong relationship is depicted with a solid line connecting the two entities.

Question 36

Existent-Dependent Entity

Accepted Answer

- also known as a composite (bridge, join, link, associative) entity  - generally used to transform M:N relationships into 1:M relationships.

Question 37

Recursive Relationship

Accepted Answer

when an entity is related to itself.

Question 38

Entity SUPERtype

Accepted Answer

- is used to minimize the likelihood of redundant relationships  - s a generic entity type that is related to one or more entity subtypes  - minimize the number of nulls  - contains the common characteristics

Question 39

Entity SUBtype

Accepted Answer

- stores data that is UNIQUE TO THE SUBTYPE

Question 40

Subtype DISCRIMINATOR

Accepted Answer

the attribute in the supertype entity that is used to determine to which entity subtype the supertype occurrence is related

Question 41

OVERLAPPING subtypes

Accepted Answer

each entity instance of the supertype may appear in more than one subtype

Question 42

PARTIAL completeness

Accepted Answer

not every supertype occurrence is a member of a subtype  - a disjointed subtype

Question 43

Entity CLUSTER

Accepted Answer

- a \"virtual\" entity type used to represent multiple entities and relationships in the ERD.  - formed by combining multiple interrelated entities into a single abstract entity object.  - used to represent multiple entities and relationships with the purpose of simplifying the ERD and thus enhancing its readability.

Question 44

Primary Key Characteristics

Accepted Answer

- Unique values: must be able to guarantee  - Nonintelligent: no embedded semantic meaning  - No Change over Time: changing value means changing identity of entity  - preferrably single-attribute: minimum # of attributes possible  - preferrably numeric: better managed that way  - security complaint: not composed of any value that could be a security risk

Question 45

Composite Primary Keys

Accepted Answer

useful for:   - composite entities (resolving M:N relationship)  - weak entities with strong relationships

Question 46

SURROGATE primary key

Accepted Answer

- used to ensure entity integrity, and by making queries simpler  - an \"artificial\" PK that is used to uniquely identify each entity occurrence when there is no good natural key available or when the \"natural\" PK would include multiple attributes.  - used to ensure that relationships between entities can be created more easily  - introduced by the designer with the purpose of simplifying the assignment of primary keys to tables.  - are usually numeric, they are often automatically generated by the DBMS, and they are free of semantic content (they have no special meaning).

Question 47

Normalization

Accepted Answer

the process for evaluating and correcting table structures to  - minimize data redundancies  - reduce likelihood of data anomalies  - minimize and/or eliminate data integrity problems

Question 48

1NF

Accepted Answer

all the key attributes are defined (no repeating groups in the table) and when all remaining attributes are dependent on the primary key

Question 49

2NF

Accepted Answer

all the key attributes are defined (no repeating groups in the table) , all remaining attributes are dependent on the primary key, and it includes no partial dependencies

Question 50

3NF

Accepted Answer

when it includes no partial dependencies and it contains no transitive dependencies

Question 51

BCNF

Accepted Answer

every determinant in the table is a candidate key.

Question 52

Partial Dependency

Accepted Answer

exists when an attribute is dependent on only a portion of the primary key.

Question 53

The most common anomalies considered when data redundancy exists are:

Accepted Answer

update, insertion, deletion anomalies

Question 54

To remove a transitive dependency, the designer must

Accepted 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 55

Why is a table whose primary key consists of a single attribute automatically in 2NF when it is in 1NF?

Accepted 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 56

TOTAL completeness

Accepted Answer

each instance of a super may appear in more than one subtype   - overlapping subtype

Question 57

Foreign Key

Accepted Answer

attribute or combination of attributes in one table whose values must match the primary key i another (parent) table or whose values must be null

Question 58

Candidate Key

Accepted Answer

minimal super-key, that is, one that does not contain a subset of attributes that is itself a supe-key

Question 59

Natural Identifier

Accepted Answer

a real-world, generally accepted identifier used to identify real world objects. familiar to end users and forms part of their day-to-day vocabulary

Question 60

Prime Attribute

Accepted Answer

key attribute that is part of a key or is the whole key.   - prime attribute = if an attribute is part of the key

Question 61

Non-Prime Attribute

Accepted Answer

attribute that is not part of a key

Question 62

ERD

Accepted Answer

- Entity Relationship Diagram   - Diagram that depicts an entity relationship model\'s entities, attributes and relations.

Question 63

CHEN

Accepted Answer

describes relationships (1:1, 1:M, and M;N) among entities at the conceptual level with the help of ER diagrams

Question 64

Crow\'s Foot

Accepted Answer

representation of the entity relationship diagram using three-pronged symbol to represent the \"many\" sides of the relationship

LIS2780 – Database Management – Flashcards

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