SQL/MP Installation and Management Guide

The SQL/MP Database Management Environment
HP NonStop SQL/MP Installation and Management Guide—523353-004
1-3
SQL Catalogs
Views
A view is a table that has a logical definition and a file label, but contains no data. A
protection view is derived from a single table by selecting a subset of the table columns
and rows. A shorthand view is derived by selecting columns and rows from one or
more tables and views.
Constraints
A constraint helps protect the integrity of data in a base table by specifying a condition
or conditions that all the values in a particular column of the table must satisfy. Unlike
other SQL objects, constraints have only SQL names, not Guardian names, and
constraints do not have external file labels.
Collations
A collation contains rules for collating sequence, upshifting, downshifting, character
class, and character string equivalence. A collation associated with a table, index, or
view column defines the default sort order for column values and shifting rules.
SQL Catalogs
An SQL/MP catalog consists of a set of tables on a single subvolume. Catalog tables
contain specific information about SQL objects and programs, such as keys,
comments, columns, partitions, attributes, and interdependencies. The catalog tables
themselves compose a normalized SQL database indexed for rapid access.
The SQL/MP catalog manager process automatically updates one or more sets of
catalog tables according to instructions in DDL statements. When you create an SQL
object, SQL/MP registers the object in an existing catalog. You can specify which
catalog is to contain the description of an object.
Each node that uses SQL/MP has a catalog called the system catalog, that contains
information about all the catalogs on the node. The system catalog is like any other
catalog, with a few exceptions (described in Requirements for Catalogs
on page 5-4).
Active Data Dictionary
An SQL/MP data dictionary is the collection of all the catalogs and associated file
labels that describe all the SQL/MP tables, views, indexes, constraints, and collations
that make up a database.
The SQL/MP data dictionary is an active dictionary. Any changes to database
definitions immediately apply to programs that use the changed portion of the
database. The data dictionary is not a passive collection of definitions but an active
part of applications. When performing database management tasks, you must be
aware of how changes affect the data dictionary.