Я получаю следующую ошибку в Oracle SQL Developer:
Error starting at line 1 in command:
ALTER TABLE AEROPUERTO ADD CONSTRAINT AEROPUERTO_FK FOREIGN KEY (CODIGO_CIUDAD) REFERENCES CIUDAD(CODIGO)
Error report:
SQL Error: ORA-02298: cannot validate (SYSTEM.AEROPUERTO_FK) - parent keys not found
02298. 00000 - "cannot validate (%s.%s) - parent keys not found"
*Cause: an alter table validating constraint failed because the table has
child records.
*Action: Obvious
Почему?