GLOSSARY - Concepts of Database Management - page 372

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Primary sort key When sorting on two fields, the
more important field; also called a major sort key .
Privacy The right of individuals to have certain infor-
mation about them kept confidential.
Private visibility In UML, an indication that only the
class itself can view or update the attribute value.
Procedural language A language in which a user
specifies the steps that are required for accomplishing
a task instead of merely describing the task itself.
Product The table obtained by concatenating every
row in the first table with every row in the
second table.
Production system The hardware, software, and
database for the users; also called live system .
PROJECT The relational algebra command used to
select columns from a table.
Protected visibility In UML, an indication that only
the class itself or public or protected subclasses of the
class can view or update the attribute value.
Public visibility In UML, an indication that any class
can view or update the attribute value.
QBE See Query-By-Example .
Qualify To indicate the table (relation) of which a
given column (attribute) is a part by preceding the
column name with the table name. For example,
Customer.Address indicates the column named
Address within the table named Customer.
Query A question, the answer to which is found in
the database; also used to refer to a command in a
nonprocedural language such as SQL that is used to
obtain the answer to such a question.
Query-By-Example (QBE) A data manipulation lan-
guage for relational databases in which users indicate
the action to be taken by completing on-screen forms.
RAID (redundant array of inexpensive/independent
drives) A device used to protect against hard drive
failures in which database updates are replicated to
multiple hard drives so that an organization can con-
tinue to process database updates after losing one of
its hard drives.
RDBMS See relational DBMS .
Record A collection of related fields; can be thought
of as a row in a table.
Recovery The process of returning a database to a
state that is known to be correct from a state known
to be incorrect.
Redundancy Duplication of data, or the storing of
the same data in more than one place.
Referential integrity The rule that if a table A con-
tains a foreign key that matches the primary key of

table B, then the value of this foreign key must either
match the value of the primary key for some row in
table B or be null.
Relation A two-dimensional table-style collection of
data in which all entries are single-valued, each col-
umn has a distinct name, all the values in a column
are values of the attribute that is identified by the col-
umn name, the order of columns is immaterial, each
row is distinct, and the order of rows is immaterial.
Also called a table .
Relational algebra A relational data manipulation
language in which new tables are created from existing
tables through the use of a set of operations.
Relational database A collection of relations (tables).
Relational DBMS (RDBMS) A DBMS that supports
and manipulates a relational database.
Relational operator An operator used to compare
values. Valid operators are=, <, >, <=, >=, <>, and !=.
Also called a comparison operator .
Relationship An association between entities.
Remote site From a user's perspective, any site other
than the one at which the user is working.
Repeating group Several entries at a single location
in a table.
Replica A copy of the data in a database that a user
can access at a remote site.
Replicate A duplicate of the data in a database that a
user can access at a remote site.
Replication transparency The property that users do
not need to be aware of any replication that has taken
place in a distributed database.
Reserved word A word that is part of the SQL
language.
REVOKE The SQL statement that is used to revoke
privileges from users of a database.
Roll up View and analyze higher levels of
aggregation.
Rollback A process to recover a database to a valid
state by reading the log for problem transactions and
applying the before images to undo their updates; also
called backward recovery .
Row-and-column subset view A view that consists of
a subset of the rows and columns in a table.
Sandbox See test system .
Sarbanes-Oxley (SOX) Act A federal law enacted in
2002 that specifies data retention and verification
requirements for public companies, requires CEOs
and CFOs to certify financial statements, and makes it
a crime to destroy or tamper with financial records.