WGU C170 Chapter 1 RATED A+
AREA - ✔✔In DB2, a named section of permanent storage space that is reserved to store the
database.
associative entity - ✔✔See composite entity.
bridge entity - ✔✔See composite entity.
candidate key - ✔✔A minimal superkey; that is, a key that does not contain a subset of attributes
that is itself a superkey. See key.
closure - ✔✔A property of relational operators that permits the use of relational algebra operators
on existing tables (relations) to produce new relations.
composite entity - ✔✔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. See also linking table.
composite key - ✔✔A multiple-attribute key.
dependent - ✔✔An attribute whose value is determined by another attribute.
determination - ✔✔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.
DIFFERENCE - ✔✔In relational algebra, an operator used to yield all rows from one table that are not
found in another union-compatible table.
DIVIDE - ✔✔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.
, domain - ✔✔In data modeling, the construct used to organize and describe an attribute's set of
possible values.
entity integrity - ✔✔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.
equijoin - ✔✔A join operator that links tables based on an equality condition that compares specified
columns of the tables.
flags - ✔✔Special codes implemented by designers to trigger a required response, alert end users to
specified conditions, or encode values. Flags may be used to prevent nulls by bringing attention to
the absence of a value in a table.
foreign key (FK) - ✔✔An attribute or attributes in one table whose values must match the primary
key in another table or whose values must be null. See key.
full functional dependence - ✔✔A condition in which an attribute is functionally dependent on a
composite key but not on any subset of the key.
functional dependence - ✔✔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 B.
homonyms - ✔✔The use of the same name to label different attributes. Homonyms generally should
be avoided. Some relational software automatically checks for homonyms and either alerts the user
to their existence or automatically makes the appropriate adjustments. See also synonym.
index - ✔✔An ordered array of index key values and row ID values (pointers). Indexes are generally
used to speed up and facilitate data retrieval. Also known as an index key.
index key - ✔✔See index.
inner join - ✔✔A join operation in which only rows that meet a given criterion are selected. The join
criterion can be an equality condition (natural join or equijoin) or an inequality condition (theta join).
The inner join is the most commonly used type of join. Contrast with outer join.
AREA - ✔✔In DB2, a named section of permanent storage space that is reserved to store the
database.
associative entity - ✔✔See composite entity.
bridge entity - ✔✔See composite entity.
candidate key - ✔✔A minimal superkey; that is, a key that does not contain a subset of attributes
that is itself a superkey. See key.
closure - ✔✔A property of relational operators that permits the use of relational algebra operators
on existing tables (relations) to produce new relations.
composite entity - ✔✔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. See also linking table.
composite key - ✔✔A multiple-attribute key.
dependent - ✔✔An attribute whose value is determined by another attribute.
determination - ✔✔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.
DIFFERENCE - ✔✔In relational algebra, an operator used to yield all rows from one table that are not
found in another union-compatible table.
DIVIDE - ✔✔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.
, domain - ✔✔In data modeling, the construct used to organize and describe an attribute's set of
possible values.
entity integrity - ✔✔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.
equijoin - ✔✔A join operator that links tables based on an equality condition that compares specified
columns of the tables.
flags - ✔✔Special codes implemented by designers to trigger a required response, alert end users to
specified conditions, or encode values. Flags may be used to prevent nulls by bringing attention to
the absence of a value in a table.
foreign key (FK) - ✔✔An attribute or attributes in one table whose values must match the primary
key in another table or whose values must be null. See key.
full functional dependence - ✔✔A condition in which an attribute is functionally dependent on a
composite key but not on any subset of the key.
functional dependence - ✔✔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 B.
homonyms - ✔✔The use of the same name to label different attributes. Homonyms generally should
be avoided. Some relational software automatically checks for homonyms and either alerts the user
to their existence or automatically makes the appropriate adjustments. See also synonym.
index - ✔✔An ordered array of index key values and row ID values (pointers). Indexes are generally
used to speed up and facilitate data retrieval. Also known as an index key.
index key - ✔✔See index.
inner join - ✔✔A join operation in which only rows that meet a given criterion are selected. The join
criterion can be an equality condition (natural join or equijoin) or an inequality condition (theta join).
The inner join is the most commonly used type of join. Contrast with outer join.
