SQL/MX Glossary

Glossary
HP NonStop SQL/MX Glossary—523732-002
Glossary-9
DDL statement
DDL statement. A statement used to define, delete, or modify the SQL definition of an
object, catalog, or to change the authorization to use the object, catalog, or schema.
Contrast with DCL statement and DML statement.
deadlock. A block to data access caused by processes contending for the same data. For
example, deadlock occurs when process A has locked one row and is waiting for
another row already locked by process B, and process B is waiting for the row already
locked by process A.
decision support application. An application that allows users to query (and possibly
update) a database to make business decisions often based on summarization or
statistical analysis of transaction data.
definitional integrity. The condition of a database when its file labels and metadata tables
contain consistent definitions of objects. Contrast with data integrity.
delimited identifier. Names consisting of character strings that appear within double
quotes ("), consisting of alphanumeric characters and other characters except for the
at sign @, forward slash /, backward slash \, circumflex ^. Delimited Identifiers are
case-sensitive. See also regular identifier.
dependency. The use of an object by another object.
dependent object. An object whose definition depends on the definition of a base or
underlying object; for example, an index is dependent on a table.
dequeue. To read and delete entries with a single operation by using a SELECT statement
with an embedded delete. This dequeue operation is sometimes referred to as a
destructive select. Alternately, a SELECT statement with an embedded update
operation allows an application to dequeue entries without actually deleting the entry
from the database table. In this case, the entries are marked for archiving.
derived column. An SQL value expression that appears as an item in the select list of a
SELECT statement. An explicit name for a derived column is an SQL identifier
associated with the derived column.
derived table. A query that is nested in the FROM clause of another query.
directive. A statement that gives instructions to a compiler.
dirty reads. Reads of data as it is modified by a concurrent process. Compare with
nonrepeatable reads and phantom reads.
disk directory. A directory that contains the file labels for each SQL table, view, and index
on a disk volume and the location of each object on the disk.
Disk Process 2 (DP2). See Data Access Manager (DAM)