看起来像 CASE 对我来说，例如。

insert into film (id_film, id_director)
select id_film,
       case when id_director = -1 then null
            else id_director
       end
from ...

行吗？对：

SQL> create table director (id number primary key);

Table created.

SQL> create table film (id number primary key, id_director number references director);

Table created.

SQL> insert into director values (100);

1 row created.

插入-1失败：

SQL> insert into film (id, id_director) values (1, -1);
insert into film (id, id_director) values (1, -1)

* 

ERROR at line 1:
ORA-02291: integrity constraint (SCOTT.SYS_C0065885) violated - parent key not
found

插入空作品：

SQL> insert into film (id, id_director) values (1, null);

1 row created.

SQL>