C170 Data Management Application
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 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.
INTERSECT - ✔✔In relational algebra, an operator used to yield only the rows that are common to
two union-compatible tables.
JOIN - ✔✔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 columns - ✔✔Columns that are used in the criteria of join operations. The join columns generally
share similar values (have a compatible domain).
key - ✔✔One or more attributes that determine other attributes. See also superkey, candidate key,
primary key (PK), secondary key, and foreign key.
key attribute - ✔✔The attributes that form a primary key. See also prime attribute.
left outer join - ✔✔In a pair of tables to be joined, a join that yields all the rows in the left table,
including those that have no matching values in the other table. For example, a left outer join of
CUSTOMER with AGENT will yield all of the CUSTOMER rows, including the ones that do not have a
matching AGENT row. See also outer join and right outer join.
linking table - ✔✔In the relational model, a table that implements an M:M relationship. See also
composite entity.
natural join - ✔✔A relational operation that yields a new table composed of only the rows with
common values in their common attribute(s).
null - ✔✔The absence of an attribute value. Note that a null is not a blank.
outer join - ✔✔Returns a set of records that include what an inner join would return but also
includes other rows for which no corresponding match is found in the other table. Contrast with
inner join. See also left outer join and right outer join.
, predicate logic - ✔✔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) - ✔✔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 - ✔✔A key attribute; that is, an attribute that is part of a key or is the whole key. See
also key attributes.
PRODUCT - ✔✔In relational algebra, an operator used to yield all possible pairs of rows from two
tables. Also known as the Cartesian product.
PROJECT - ✔✔In relational algebra, an operator used to select a subset of columns.
referential integrity - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔See SELECT.
right outer join - ✔✔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 - ✔✔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.
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 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.
INTERSECT - ✔✔In relational algebra, an operator used to yield only the rows that are common to
two union-compatible tables.
JOIN - ✔✔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 columns - ✔✔Columns that are used in the criteria of join operations. The join columns generally
share similar values (have a compatible domain).
key - ✔✔One or more attributes that determine other attributes. See also superkey, candidate key,
primary key (PK), secondary key, and foreign key.
key attribute - ✔✔The attributes that form a primary key. See also prime attribute.
left outer join - ✔✔In a pair of tables to be joined, a join that yields all the rows in the left table,
including those that have no matching values in the other table. For example, a left outer join of
CUSTOMER with AGENT will yield all of the CUSTOMER rows, including the ones that do not have a
matching AGENT row. See also outer join and right outer join.
linking table - ✔✔In the relational model, a table that implements an M:M relationship. See also
composite entity.
natural join - ✔✔A relational operation that yields a new table composed of only the rows with
common values in their common attribute(s).
null - ✔✔The absence of an attribute value. Note that a null is not a blank.
outer join - ✔✔Returns a set of records that include what an inner join would return but also
includes other rows for which no corresponding match is found in the other table. Contrast with
inner join. See also left outer join and right outer join.
, predicate logic - ✔✔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) - ✔✔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 - ✔✔A key attribute; that is, an attribute that is part of a key or is the whole key. See
also key attributes.
PRODUCT - ✔✔In relational algebra, an operator used to yield all possible pairs of rows from two
tables. Also known as the Cartesian product.
PROJECT - ✔✔In relational algebra, an operator used to select a subset of columns.
referential integrity - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔See SELECT.
right outer join - ✔✔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 - ✔✔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.
