Oracle Error ORA-22894: cannot add constraint on existing unscoped REF columns of non-empty tables

Oracle Error Message

ORA-22894: cannot add constraint on existing unscoped REF columns of non-empty tables

Reason for the Error

An attempt was made to add a constraint to existing unscoped REF columns of a table which contains one or more rows.

Solution

Remove the constraint specification or add the constraint after emptying the table.