C170 DATA MANAGEMENT SCRIPT
COMPLETE ANSWERS GRADED A+
◉ 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.
COMPLETE ANSWERS GRADED A+
◉ 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.
