Database Reference
In-Depth Information
Database Design Language (DBDL) A relational-like
language that is used to represent the result of the
database design process.
Database management system (DBMS) A program, or a
collection of programs, through which users interact
with a database. DBMSs let you create forms and
reports quickly and easily, as well as obtain answers to
questions about the data stored in a database.
Database password A string of characters assigned by
the DBA to a database that users must enter before they
can access a database.
Database server In a three-tier client/server
architecture and in other architectures, a computer
that performs the database functions such as storing
and retrieving data in a database.
Datasheet form A form layout that displays data in a
datasheet format.
DATE The SQL data type for date data.
DBA See database administration. (Sometimes the
acronym stands for database administrator.)
DBDL See Database Design Language.
DBMS See database management system.
DDBMS See distributed database management system.
Deadlock A situation in which two or more database
users are each waiting to use resources that are held by
the other(s); also called deadly embrace.
Deadly embrace See deadlock.
DECIMAL(p,q) The SQL data type for decimal data.
Decrypting A process that reverses the encryption of a
database. Also called decryption.
Defining query The query that is used to define the
structure of a view.
DELETE The SQL command used to delete a table. The
word DELETE is followed by a FROM clause identifying
the table. Use a WHERE clause to specify a condition.
Any records satisfying the condition will be deleted.
Delete query A query that deletes all records that
satisfy some criterion.
Delimiter A punctuation mark, such as a semicolon,
that separates pieces of data.
Denormalizing The conversion of a table that is in third
normal form to a table that is no longer in third normal
form. Denormalizing introduces anomaly problems but
can decrease the number of disk accesses required
by certain types of transactions, thus improving
performance.
Department of Defense (DOD) 5015.2 Standard A
standard that provides data management requirements
for the DOD and for companies supplying or dealing
with the DOD.
Dependency diagram A diagram that indicates the
dependencies among the columns in a table.
Dependent entity An entity that requires a relationship
to another entity for identification.
Design grid The portion of the Query Design window in
Access where you enter fields, criteria, sort orders, and
so on.
Determinant A column in a table that determines at
least one other column.
Difference When comparing tables, the set of all rows
that are in the first table but that are not in the second
table.
Dimension table A table in a data warehouse that
contains a single-part primary key, serving as an index
into the central fact table, and other fields associated
with the primary key value.
Disaster recovery plan A plan that specifies the ongoing
and emergency actions and procedures required to
ensure data availability, even if a disaster occurs.
Distributed database A single logical database that is
physically divided among computers at several sites on a
computer network.
Distributed database management system (DDBMS) A
DBMS capable of supporting and manipulating distrib-
uted databases.
Division The relational algebra command that com-
bines tables and searches for rows in the first table that
match all rows in the second table.
Document Type Definition (DTD) A set of statements
that specifies the elements (tags), the attributes (char-
acteristics associated with each tag), and the element
relationships for an XML document. The DTD can be a
separate file with a .dtd extension, or you can include it
at the beginning of an XML document.
Documenter An Access tool that provides documenta-
tion about the objects in a database.
Domain The set of values that are permitted for an
attribute.
Drill down The process of viewing and analyzing lower
levels of aggregation, or a more detailed view of the data.
DROP INDEX The SQL command that drops (deletes)
an index from a table.
DROP TABLE The SQL command that drops (deletes)
a table from a database.
DTD See Document Type Definition.
Dynamic Web page A Web page whose content changes
in response to the different inputs and choices made by
Web clients.
E-commerce See electronic commerce.
Electronic commerce (e-commerce) Business con-
ducted on the Internet and Web.
Encapsulated In an object-oriented system, defining an
object to contain both data and its associated actions.
Encryption A security measure that converts the data
in a database to a format that's indecipherable to normal
programs. The DBMS decrypts, or decodes, the data to
its original form for any legitimate user who accesses the
database.
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