ORA-02291: integrity constraint (string.string)
violated - parent key not found
Cause: A foreign
key value has no matching primary key value.
Delete the foreign key or add a matching primary key.
For an insert statement, this ORA-02291 error
is common when you are trying to insert a child without a
matching parent, as defined by a foreign key constraint.
In that case, you need to add the parent row to the table and
then re-insert your child table row.
dba_constraints view to find the parent table.
fully understand [primary and foreign key constraints, see the
Easy Oracle Jumpstart, to explain these concepts: