WGU C170 DATA MANAGEMENT
APPLICATIONS COMPLETE STUDY GUIDE 2026
◉ outer join. Answer: A relational algebra join operation that
produces a table in which all unmatched pairs are retained;
unmatched values in the related table are left null. Contrast with
inner join. See also left outer join and right outer join.
◉ predicate logic. Answer: Used extensively in mathematics to
provide a framework in which an assertion (statement of fact) can
be verified as either true or false.
◉ primary key (PK). Answer: 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. See also
key.
◉ prime attribute. Answer: A key attribute; that is, an attribute that
is part of a key or is the whole key. See also key attributes.
◉ PRODUCT. Answer: In relational algebra, an operator used to yield
all possible pairs of rows from two tables. Also known as the
Cartesian product.
,◉ PROJECT. Answer: In relational algebra, an operator used to select
a subset of columns.
◉ referential integrity. Answer: A condition by which a dependent
table's foreign key must have either a null entry or a matching entry
in the related table.
◉ relational algebra. Answer: 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.
◉ relvar. Answer: Short for relation variable, a variable that holds a
relation. A relvar is a container (variable) for holding relation data,
not the relation itself.
◉ RESTRICT. Answer: See SELECT.
◉ right outer join. Answer: In a pair of tables to be joined, a join that
yields all of the rows in the right table, including the ones with no
matching values in the other table. For example, a right outer join of
CUSTOMER with AGENT will yield all of the AGENT rows, including
the ones that do not have a matching CUSTOMER row. See also left
outer join and outer join.
, ◉ secondary key. Answer: 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. See also key.
◉ SELECT. Answer: (1) A SQL command that yields the values of all
rows or a subset of rows in a table. The SELECT statement is used to
retrieve data from tables. (2) In relational algebra, an operator to
select a subset of rows. Also known as RESTRICT.
◉ set theory. Answer: 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.
◉ superkey. Answer: An attribute or attributes that uniquely identify
each entity in a table. See key.
◉ synonym. Answer: The use of different names to identify the same
object, such as an entity, an attribute, or a relationship; synonyms
should generally be avoided. See also homonym.
◉ system catalog. Answer: A detailed system data dictionary that
describes all objects in a database.
APPLICATIONS COMPLETE STUDY GUIDE 2026
◉ outer join. Answer: A relational algebra join operation that
produces a table in which all unmatched pairs are retained;
unmatched values in the related table are left null. Contrast with
inner join. See also left outer join and right outer join.
◉ predicate logic. Answer: Used extensively in mathematics to
provide a framework in which an assertion (statement of fact) can
be verified as either true or false.
◉ primary key (PK). Answer: 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. See also
key.
◉ prime attribute. Answer: A key attribute; that is, an attribute that
is part of a key or is the whole key. See also key attributes.
◉ PRODUCT. Answer: In relational algebra, an operator used to yield
all possible pairs of rows from two tables. Also known as the
Cartesian product.
,◉ PROJECT. Answer: In relational algebra, an operator used to select
a subset of columns.
◉ referential integrity. Answer: A condition by which a dependent
table's foreign key must have either a null entry or a matching entry
in the related table.
◉ relational algebra. Answer: 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.
◉ relvar. Answer: Short for relation variable, a variable that holds a
relation. A relvar is a container (variable) for holding relation data,
not the relation itself.
◉ RESTRICT. Answer: See SELECT.
◉ right outer join. Answer: In a pair of tables to be joined, a join that
yields all of the rows in the right table, including the ones with no
matching values in the other table. For example, a right outer join of
CUSTOMER with AGENT will yield all of the AGENT rows, including
the ones that do not have a matching CUSTOMER row. See also left
outer join and outer join.
, ◉ secondary key. Answer: 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. See also key.
◉ SELECT. Answer: (1) A SQL command that yields the values of all
rows or a subset of rows in a table. The SELECT statement is used to
retrieve data from tables. (2) In relational algebra, an operator to
select a subset of rows. Also known as RESTRICT.
◉ set theory. Answer: 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.
◉ superkey. Answer: An attribute or attributes that uniquely identify
each entity in a table. See key.
◉ synonym. Answer: The use of different names to identify the same
object, such as an entity, an attribute, or a relationship; synonyms
should generally be avoided. See also homonym.
◉ system catalog. Answer: A detailed system data dictionary that
describes all objects in a database.
