Annotating a constraint

Stereotypes on a constraint

The stereotypes used to annotate constraints are presented in the following table:

The ... stereotype	is used to...	SQL
<<notNull>>	indicate that the column must have a value.	NOT NULL
<<null>>	indicate the column may not have a value.	NULL
<<unique>>	Indicate that the values taken by the attribute must be unique for the entire table.	UNIQUE
<<check>>	associate a "check" type constraint to an attribute.	CHECK
<<rule>>	associate a "rule" type constraint to an attribute (Sybase).	CREATE RULE
<<doNotGenerate>>	indicate that an attribute or a column will not be handled by the generation operation.	N/A

The <<notNull>> stereotype

The <<notNull>> stereotype is used for constraints on attributes. It indicates that the attribute must be valued.

The <<null>> stereotype

The <<null>> stereotype is used for constraints on attributes. It indicates that the column cannot be valued. This stereotype imposes the generation of a "NULL" constraint in the column corresponding to the attribute. It allows the use of an "undetermined" when inserting a tuple for which data has not been entered in the column.

The <<unique>> stereotype

The <<unique>> stereotype is used for constraints on attributes. It indicates that the values taken by the attribute must be unique for the entire table.

The <<check>> stereotype

The <<check>> stereotype is used for constraints on attributes, and is used to associate a <<check>> type constraint to an attribute.
The <<check>> constraint allows the specification of a Boolean expression that will have to be checked, in order for a tuple to be inserted into the table.

This constraint has as its body the logical condition, used as is, for building the clause's SQL. We recommend that you place this body between inverted commas for the syntactical analyzer. For example:

{check} ("(att1 + att2) between 1 and 12")

Note: Remember in this case that if you wish to incorporate the " character into the text, you must enter the ~ character before it.

The <<rule>> stereotype

The <<rule>> stereotype is used to associate a "rule" type constraint to an attribute (Sybase only).

The <<doNotGenerate>> stereotype

The <<doNotGenerate>> stereotype indicates that an attribute will not be taken into account during the transformation of the object model into a physical model, and that a column will not be taken into account during the generation of SQL code from the physical model.