| A table constraint is either a unique constraint, a referential constraint or a table check constraint. A table constraint is described by a table constraint descriptor which is either a unique constraint descriptor, a referential constraint descriptor or a table check constraint descriptor. |
| Every table constraint specified for base table T is implicitly a constraint on every subtable of T, by virtue of the fact that every row in a subtable is considered to have a corresponding superrow in every one of its supertables. |
