SQL/MX 3.2.1 Management Manual (H06.26+, J06.15+)

Table 2 SQL/MX Object Types (continued)
DescriptionSQL/MX Object Type
particular record. Every table must have one or more columns, but the number of
rows can be zero. There is no inherent order of rows within a table.
An SQL/MX table is described in an SQL/MX schema and its data is stored in one
or more physical files in the Guardian environment. An SQL/MX table name must
be a fully qualified ANSI name of the form:
catalog-name.schema-name.object-name
A table that has a logical name and an associated physical file that resides in the
Guardian environment. A view is derived from a query that determines how to create
View
the view contents from other tables or views. SQL/MX views conform to the
ANSI/ISO/IEC 9075:1999 SQL standard, more commonly referred to as SQL:1999,
for their definition and security.
An alternate access path to a table (alternate key) that differs from the primary access
path (clustering key) defined when the table was created. An SQL/MX index includes
columns for the alternate key and the underlying table’s clustering key.
Index
A stored procedure is an type of user-defined routine (UDR) that operates within a
database server. NonStop SQL/MX supports stored procedures written in the Java
Stored procedures in Java (SPJs)
language (SPJs). The body of an SPJ is a static Java method, which is stored in a
class file either inside or outside a Java archive (JAR) file in the OSS file system. An
SPJ is registered in NonStop SQL/MX and invoked by NonStop SQL/MX when an
application issues a CALL statement.
For more information, see the SQL/MX Guide to Stored Procedures in Java.
Constraints protect the integrity of data in a table by restricting the values in a
particular column or set of columns to those that meet specified conditions. The
SQL/MX constraints are:
Constraints
• Not Null, which is a constraint that identifies the column or columns that cannot
contain nulls.
• Unique, which is a column or table constraint that identifies the column or set of
columns that cannot contain more than one occurrence of the same value or set
of values.
• Primary key, which is a column or table constraint that identifies the column or
set of columns that constitute the primary key for a table. A primary key is also
a unique key.
• Check, which is a column or table constraint that identifies the condition that must
be satisfied for each row in a table. Check constraints cannot contain
non-ISO88591 string literals.
• Referential integrity, which identifies the column or columns in a table that can
contain only values matching those in a column or set of columns in the referenced
table.
A three-part ANSI name that maps to the underlying Guardian physical name of an
SQL/MP object.
SQL/MP alias
A mechanism that resides in the database and specifies that when a particular
operation—an INSERT, DELETE, or UPDATE—is performed on a particular table,
NonStop SQL/MX should automatically perform one or more additional actions.
Trigger
The portion of a partitioned table or index that resides in a single physical Guardian
file. Multiple partitions can reside on the same disk volume. A table that has only
one partition is a nonpartitioned table.
Partition
A sequence generator is a database object that generates unique sequential values.
For example, you can use sequence generators to generate primary key values. After
Sequence Generator
a number is generated, the sequence generator is incremented for ascending
sequence and decremented for descending sequence.
After a sequence generator is created, you can access its values in SQL statements
using the CURRVAL pseudocolumn, which returns the current value of the sequence,
or the NEXTVAL pseudocolumn, which increments or decrements the sequence and
returns the new value.
For more information, see the SQL/MX Reference Manual.
SQL/MX Database Object Types 25