A component specification in an SQL statement specifies the attribute of a member of an abstract data type, defined in the abstract data type.
component-specification::=item-specification..attribute-name [..attribute-name]...
A component specification is subject to the following rules:
- If a value is assigned to an attribute, the value of the abstract data type containing the attribute must be generated by the constructor function (the value of the abstract data type cannot be the null value).
- If an attribute is referenced by means of a component specification and the abstract data type containing the attribute is null (if that value was not generated by the constructor function), the referenced value will also be null.
- A subscripted column specification cannot be specified in an item specification.