Attribute annotations

Tagged values

The tagged values available at attribute level are presented in the following table:

The ... tagged value	is used to ...	Oracle
{check}	declare a "check" type constraint in the column associated to the attribute in question.	CHECK
{default}	give the default value in the column	DEFAULT
{null}	specify that the column is NULL type	NULL
{unique}	declare that the column as unique	UNIQUE

The {check} tagged value

The {check} tagged value allows the specification of a Boolean expression in a column, which will have to be checked so that a tuple is inserted in the table.

See the {check} tagged value on classes for further details.

The {null} tagged value

This tagged value imposes the generation of a "NULL" constraint in the column corresponding to the attribute.

This constraint allows the use of an "undetermined" when inserting a tuple, for which data has not been entered in the column.