Midterms Database Flashcards
Used extensively in mathematics to provide a framework in which an assertion
(statement of fact) can be verified as either true or false
predicate logic
A part of mathematical science that deals with sets, or groups of things, and is used as
the basis for data manipulation in the relational model
set theory
is perceived as a two-dimensional structure composed of rows and columns.
table
related entity occurrences
entity set
In the relational model, a table row.
tuple
In data modeling, the construct used to organize and describe an attribute’s set of
possible values.
attribute domain
_______ are sometimes referred to as records, and _______ are sometimes labeled as
fields. Occasionally, tables are _______
rows , columns , labeled files
. You can use numeric data to perform meaningful arithmetic procedures.
Numeric
also known as text data or string data, can contain any
character or symbol not intended for mathematical manipulation.
Character
attributes contain calendar dates stored in a special format known as the
Julian date format.
Date
can only have true or false (yes or no) values
Logical
consists of one or more attributes that determine other attributes.
key
is the state in which knowing the value of one attribute makes it possible
to determine the value of another.
Determination
The relationship is called________ which means that the value of one or
more attributes determines the value of one or more other attributes.
functional dependence,
In the relational model, an identifier composed of one or more attributes that uniquely
identifies a row. Also, a candidate key selected as a unique entity identifier.
primary key (PK)
One or more attributes that determine other attributes.
key
The role of a key. In the context of a database table, the statement “A determines B”
indicates that knowing the value of attribute A means that the value of attribute B can be
looked up.
determination
Within a relation R, an attribute B is functionally dependent on an attribute A if and only
if a given value of attribute A determines exactly one value of attribute B. The
relationship “B is dependent on A” is equivalent to “A determines B” and is written as A
S B.
functional dependence
Any attribute in a specific row whose value directly determines other values in that row.
See also Boyce-Codd normal form (BCNF).ute in a specific row whose value directly determines other values in that row.
See also Boyce-Codd normal form (BCNF).
determinant determinant
An attribute whose value is determined by another attribute.
dependent
An attribute that is a part of a key
key attribute
A condition in which an attribute is functionally dependent on a composite key but not
on any subset of the key.
full functional dependence
is a key that is composed of more than one attribute
composite key
An attribute or attributes that uniquely identify each entity in a table.
superkey
A minimal superkey; that is, a key that does not contain a subset of attributes that is
itself a superkey.
candidate key
The property of a relational table that guarantees each entity has a unique value in a
primary key and that the key has no null values.
entity integrity
The absence of an attribute value. Note that a null is not a blank.
null
An attribute or attributes in one table whose values must match the primary key in
another table or whose values must be null
foreign key (FK)
A condition by which a dependent table’s foreign key must have either a null entry or a
matching entry in the related table.
referential integrity
A key used strictly for data retrieval purposes. For example, customers are not likely to
know their customer number (primary key), but the combination of last name, first name,
middle initial, and telephone number will probably match the appropriate table row
secondary key
Special codes implemented by designers to trigger a required response, alert end users
to specified conditions, or encode values.
may be used to prevent nulls by
bringing attention to the absence of a value in a table
flags
A set of mathematical principles that form the basis for manipulating relational table
contents; the eight main functions are SELECT, PROJECT, JOIN, INTERSECT, UNION,
DIFFERENCE, PRODUCT, and DIVIDE.
relational algebra
Short for relation variable, a variable that holds a relation.
is a container
(variable) for holding relation data, not the relation itself.
relvar
A property of relational operators that permits the use of relational algebra operators on
existing tables (relations) to produce new relations.
closure
In relational algebra, an operator used to select a subset of rows. Also known as
RESTRICT.
SELECT
In relational algebra, an operator used to select a subset of columns.
PROJECT
In relational algebra, an operator used to merge (append) two tables into a new table,
dropping the duplicate rows. The tables must be union-compatible.
UNION
Two or more tables that have the same number of columns and the corresponding
columns have compatible domains
union-compatible
In relational algebra, an operator used to yield only the rows that are common to two
union-compatible tables.
INTERSECT
In relational algebra, an operator used to yield all rows from one table that are not
found in another union-compatible table.
DIFFERENCE
In relational algebra, an operator used to yield all possible pairs of rows from two tables.
Also known as the Cartesian product
PRODUCT
In relational algebra, a type of operator used to yield rows from two tables based on
criteria. There are many types of joins, such as natural join, theta join, equijoin, and
outer join.
JOIN ( ⋈ )
A relational operation that yields a new table composed of only the rows with common
values in their common attribute(s).
natural join
Columns that are used in the criteria of join operations. The join columns generally
share similar values.
join columns
A join operator that links tables based on an equality condition that compares specified
columns of the tables.
equijoin
A join operator that links tables using an inequality comparison operator (<, >, <=, >=) in
the join condition.
theta join
A join operation in which only rows that meet a given criterion are selected. The criterion
can be an equality condition (natural join or equijoin) or an inequality condition (theta
join). The most commonly used type of join.
inner join
A join operation that produces a table in which all unmatched pairs are retained;
unmatched values in the related table are left null.
outer join
A join operation that yields all the rows in the left table, including those that have no
matching values in the other table.
left outer join
A join operation that yields all of the rows in the right table, including the ones with no
matching values in the other table
right outer join
In relational algebra, an operator that answers queries about one set of data being
associated with all values of data in another set of data.
DIVIDE
A DBMS component that stores metadata—data about data. Thus, the data dictionary
contains the data definition as well as their characteristics and relationships.
may also include data that are external to the DBMS. Also known as an
information resource dictionary.
data dictionary
A detailed system data dictionary that describes all objects in a database.
system catalog
The use of the same name to label different attributes.
generally should be
avoided.
homonym
The use of different names to identify the same object, such as an entity, an attribute, or
should generally be avoided.
synonym
_________ is the relational modeling ideal. Therefore, this relationship
type should be the norm in any relational database design.
________ should be rare in any relational database design.
●________ cannot be implemented as such in the relational model
is the norm for relational databases.
_________ - one entity in a 1:1 relationship can be related to only one other entity, and vice versa.
___________ is not supported directly in the relational
environment. However, it can be implemented by creating a new entity
in 1:M relationships with the original entity
● The 1:M relationship
● The1:1relationship
M:Nrelationships
The 1:M Relationship
The 1:1 Relationship
The M:N Relationship
An entity designed to transform an M:N relationship into two 1:M relationships. The
composite entity’s primary key comprises at least the primary keys of the entities that it
connects.
Also known as a bridge entity or associative entity.
composite entity
In the relational model, a table that implements an M:M relationship.
linking table
An ordered array of index key values and row ID values (pointers).
are
generally used to speed up and facilitate data retrieval. Also known as an index key.
index
An index in which the index key can have only one associated pointer value (row)
unique index
A combination of attributes that uniquely identifies each row in a table.
It may contain redundant attributes
.Superkey
A minimal superkey, meaning it doesn’t contain any unnecessary attributes.
It is a superkey that cannot be further reduced.
Candidate Key
A candidate key selected to uniquely identify each row in a table.
It cannot contain null values.
It is typically chosen for its efficiency and ease of use.
Primary Key
An attribute or combination of attributes in one table that references the primary key of another table.
It establishes a relationship between two tables.
It ensures data integrity and consistency.
Foreign Key
An attribute or combination of attributes used for efficient data retrieval.
It is not unique, but it can be used to index the table for faster searching.
Secondary Key
The possible set of values for a given attribute. required attribute In ER modeling, an
attribute that must have a value. In other words, it cannot be left empty.
domain
In ER modeling, an attribute that does not require a value; therefore, it can be left
empty.
optional attribute
One or more attributes that uniquely identify each entity instance.
identifier
The organization of a relational database as described by the database administrator.
relational schema
In ER modeling, a key composed of more than one attribute.
composite identifier
An attribute that can be further subdivided to yield additional attributes. For example, a
phone number such as 615-898- 2368 may be divided into an area code (615), an
exchange number (898), and a four-digit code (2368).
composite attribute
An attribute that cannot be subdivided into meaningful components. Compare to
composite attribute.
simple attribute
An attribute that can have only one value.
single-valued attribute
An attribute that can have many values for a single entity occurrence. For example, an
EMP_ DEGREE attribute might store the string “BBA, MBA, PHD” to indicate three
different degrees held.
multivalued attribute
An attribute that does not physically exist within the entity and is derived via an
algorithm. For example, the Age attribute might be derived by subtracting the birth date
from the current date.
derived attribute
An ER term for entities that participate in a relationship. For example, in the relationship
“PROFESSOR teaches CLASS,” the teaches relationship is based on the participants
PROFESSOR and CLASS.
participants
The classification of the relationship between entities. Classifications include 1:1, 1:M,
and M:N.
connectivity
A property that assigns a specific value to connectivity and expresses the range of
allowed entity occurrences associated with a single occurrence of the related entity.
cardinality
A property of an entity whose existence depends on one or more other entities. In such
an environment, the existence-independent table must be created and loaded first
because the existence-dependent key cannot reference a table that does not yet exist.
existence-dependent
A property of an entity that can exist apart from one or more related entities. Such a
table must be created first when referencing an existence-dependent table.
existence-independent
An entity that is existence-independent, that is, it can exist apart from all of its related
entities.
strong entity
See strong entity
regular entity
A relationship in which the primary key of the related entity does not contain a primary
key component of the parent entity.
weak (nonidentifying) relationship
A relationship that occurs when two entities are existence-dependent; from a database
design perspective, this relationship exists whenever the primary key of the related
entity contains the primary key of the parent entity
strong (identifying) relationship
An entity that displays existence dependence and inherits the primary key of its parent
entity. For example, a DEPENDENT requires the existence of an EMPLOYEE.
weak entity
In ER modeling, a condition in which one entity occurrence does not require a
corresponding entity occurrence in a particular relationship.
optional participation
A relationship in which one entity occurrence must have a corresponding occurrence in
another entity. For example, an EMPLOYEE works in a DIVISION. (A person cannot be
an employee without being assigned to a company’s division.)
mandatory participation
The number of entities or participants associated with a relationship. A relationship
degree can be unary, binary, ternary, or higher.
unary relationship
An ER term used to describe an association within an entity. For example, an
EMPLOYEE might manage another EMPLOYEE.
binary relationship
An ER term for an association (relationship) between two entities. For example,
PROFESSOR teaches CLASS.
ternary relationship
An ER term used to describe an association (relationship) between three entities. For
example, a DOCTOR prescribes a DRUG for a PATIENT.
relationship degree
An ER term used to describe an association within an entity. For example, an
EMPLOYEE might manage another EMPLOYEE.
unary relationship
An ER term for an association (relationship) between two entities. For example,
PROFESSOR teaches CLASS.
binary relationship
An ER term used to describe an association (relationship) between three entities. For
example, a DOCTOR prescribes a DRUG for a PATIENT.
ternary relationship
A relationship found within a single entity type. For example, an EMPLOYEE is married
to an EMPLOYEE or a PART is a component of another PART.
recursive relationship
A process based on repetition of steps and procedures.
iterative process
Acronyms
● DBMS-Database Management System
● RDBMS-relational database management system
● SQL-Structured Query Language
● UML-Unified Modeling Languag
