SQL/MX 2.x Reference Manual (H06.04+)

Metadata Tables
HP NonStop SQL/MX Reference Manual—540440-003
10-40
Constraint Droppable Options
For more information, see the description for the individual attribute.
Constraint Droppable Options
These table entries describe settings that enable NonStop SQL/MX to ensure that the
defaults for certain constraints are set to NOT DROPPABLE:
These settings affect the way NonStop SQL/MX processes NOT NULL and PRIMARY
KEY constraints, as follows:
•
If a column is defined with the NOT NULL NOT DROPPABLE constraint, the
executor does not check for null—thereby improving performance of updates and
inserts. The NOT NULL NOT DROPPABLE constraint also eliminates the need for
a null indicator, which reduces space requirements.
•
If a column or a column list within a table is defined with the PRIMARY KEY NOT
DROPPABLE constraint, the primary key column or column list can be used as a
storage key—the most efficient method for partitioning by values of a unique key.
In this case, a separate index is not required for the primary key.
UPD_SAVEPOINT_ON_ERROR Controls whether DP2
savepoints should be
used and if the transaction
should be aborted in case
of an error.
Statement Atomicity on
page 10-64
VARCHAR_PARAM_
DEFAULT_SIZE
Controls the allowable
length of a LIKE
predicate.
Table Management on
page 10-67
ZIG_ZAG_TREES
Enables or disables the
optimizer to consider zig-
zag trees in addition to
linear trees.
Query Optimization and
Performance on
page 10-54
Attribute Setting
NOT_NULL_CONSTRAINT_
DROPPABLE_OPTION
Set to ON (DROPPABLE) or OFF (NOT DROPPABLE).
This option is used if DROPPABLE or NOT
DROPPABLE does not appear in the definition of a NOT
NULL column constraint.
The default is OFF.
PRIMARY_KEY_CONSTRAINT_
DROPPABLE_OPTION
Set to ON (DROPPABLE) or OFF (NOT DROPPABLE).
This option is used if DROPPABLE or NOT
DROPPABLE does not appear in the definition of a
PRIMARY KEY constraint.
The default is OFF.
Attribute Description Category