C170 QUESTIONS AND ANSWERS
LATEST UPDATE
Access plan
A set of instructions generated at application compilation time that is created and
managed by a DBMS. The access plan predetermines how an application's query will
access the database at run time.
Alias
An alternative name for a column or table in a SQL statement.
ALTER TABLE
The SQL command used to make changes to table structure. When the command is
followed by a keyword (ADD or MODIFY), it adds a column or changes column
characteristics.
AREA
In DB2, a named section of permanent storage space that is reserved to store the
database.
Atomic attribute
An attribute that cannot be further subdivided to produce meaningful components. For
example, a person's last name attribute cannot be meaningfully subdivided.
Atomicity
The transaction property that requires all parts of a transaction to be treated as a single,
indivisible, logical unit of work. All parts of a transaction must be completed or the entire
transaction is aborted.
automatic query optimization
A method by which a DBMS finds the most efficient access path for the execution of a
query.
B-tree index
An ordered data structure organized as an upside-down tree.
Base tables
Tables on which the view is based
batch update routine
A routine that pools transactions into a single batch to update a master table in a single
operation.
BETWEEN
In SQL, a special comparison operator used to check whether a value is within a range
of specified values.
binary relationship
An ER term for an association (relationship) between two entities. For example,
PROFESSOR teaches CLASS.
Bitmap index
An index that uses a bit array (0s and 1s) to represent the existence of a value or
condition.
, Boolean Algebra
A branch of mathematics that uses the logical operators OR, AND, and NOT.
Boyce-Codd Normal Form (BCNF)
A special type of third normal form (3NF) in which every determinant is a candidate key.
A table in BCNF must be in 3NF. See also determinant.
Candidate Key
A minimal superkey; that is, a key that does not contain a subset of attributes that is
itself a superkey.
Cardinality
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.
Cascading order sequence
A nested ordering sequence for a set of rows, such as a list in which all last names are
alphabetically ordered and, within the last names, all first names are ordered.
Closure
A property of relational operators that permits the use of relational algebra operators on
existing tables (relations) to produce new relations.
Composite Attribute
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). Compare to simple attribute.
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. See also linking table.
Composite Identifier
In ER modeling, a key composed of more than one attribute.
Composite Key
A multiple-attribute key.
Correlated Subquery
A subquery that executes once for each row in the outer query.
COUNT
A SQL aggregate function that outputs the number of rows containing not null values for
a given column or expression, sometimes used in conjunction with the DISTINCT
clause.
CREATE INDEX
A SQL command that creates indexes on the basis of a selected attribute or attributes.
CREATE TABLE
A SQL command that creates a table's structures using the characteristics and
attributes given.
CREATE VIEW
A SQL command that creates a logical, "virtual" table based on stored end-user tables.
The view can be treated as a real table.
Cross Join
A join that performs a relational product (or Cartesian product) of two tables.
Data Cache
LATEST UPDATE
Access plan
A set of instructions generated at application compilation time that is created and
managed by a DBMS. The access plan predetermines how an application's query will
access the database at run time.
Alias
An alternative name for a column or table in a SQL statement.
ALTER TABLE
The SQL command used to make changes to table structure. When the command is
followed by a keyword (ADD or MODIFY), it adds a column or changes column
characteristics.
AREA
In DB2, a named section of permanent storage space that is reserved to store the
database.
Atomic attribute
An attribute that cannot be further subdivided to produce meaningful components. For
example, a person's last name attribute cannot be meaningfully subdivided.
Atomicity
The transaction property that requires all parts of a transaction to be treated as a single,
indivisible, logical unit of work. All parts of a transaction must be completed or the entire
transaction is aborted.
automatic query optimization
A method by which a DBMS finds the most efficient access path for the execution of a
query.
B-tree index
An ordered data structure organized as an upside-down tree.
Base tables
Tables on which the view is based
batch update routine
A routine that pools transactions into a single batch to update a master table in a single
operation.
BETWEEN
In SQL, a special comparison operator used to check whether a value is within a range
of specified values.
binary relationship
An ER term for an association (relationship) between two entities. For example,
PROFESSOR teaches CLASS.
Bitmap index
An index that uses a bit array (0s and 1s) to represent the existence of a value or
condition.
, Boolean Algebra
A branch of mathematics that uses the logical operators OR, AND, and NOT.
Boyce-Codd Normal Form (BCNF)
A special type of third normal form (3NF) in which every determinant is a candidate key.
A table in BCNF must be in 3NF. See also determinant.
Candidate Key
A minimal superkey; that is, a key that does not contain a subset of attributes that is
itself a superkey.
Cardinality
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.
Cascading order sequence
A nested ordering sequence for a set of rows, such as a list in which all last names are
alphabetically ordered and, within the last names, all first names are ordered.
Closure
A property of relational operators that permits the use of relational algebra operators on
existing tables (relations) to produce new relations.
Composite Attribute
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). Compare to simple attribute.
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. See also linking table.
Composite Identifier
In ER modeling, a key composed of more than one attribute.
Composite Key
A multiple-attribute key.
Correlated Subquery
A subquery that executes once for each row in the outer query.
COUNT
A SQL aggregate function that outputs the number of rows containing not null values for
a given column or expression, sometimes used in conjunction with the DISTINCT
clause.
CREATE INDEX
A SQL command that creates indexes on the basis of a selected attribute or attributes.
CREATE TABLE
A SQL command that creates a table's structures using the characteristics and
attributes given.
CREATE VIEW
A SQL command that creates a logical, "virtual" table based on stored end-user tables.
The view can be treated as a real table.
Cross Join
A join that performs a relational product (or Cartesian product) of two tables.
Data Cache
