mysql - 错误代码 : 1822. 添加外键约束失败。引用表 'ekdromes_ibfk_1' 中缺少约束 'pwlhseis' 的索引

Question

我有这两张表:

create table pwlhseis(
ma int,
hmeromhnia date,
wra time,
hmer_diek date,
ae_po int,
amka_po int,
constraint foreign key (amka_po) references pelates(amka),
primary key (ma));

和:

create table ekdromes(
ae int,
diarkeia int,
proorismos varchar(20),
kostos float,
timh float,
afeteria varchar(20),
hm_enarkshs date,
primary key (ae));

然后:

alter table ypallhloi 
  add constraint foreign key (arithmos_up) references grafeia(arithmos_g);

alter table ekdromes 
  add constraint foreign key (ae) references pwlhseis(ae_po);

第一个 alter 运行良好，当我尝试运行第二个时，出现 1822 错误。有什么问题？

Answer 1

您已将主键定义为 pwlhseis(ma)。这就是您应该用于外键引用的内容。

就个人而言，我将主键和外键命名为匹配，因此，这看起来像:

create table pwlhseis (
    pwlhseis_id int primary key,
    . . .
);

create table ekdromes (
    ekdromes_id int primary key,
    . . .
    pwlhseis_id int,
);

alter table ekdromes 
  add constraint fk_ekdromes_pwlhseis foreign key (pwlhseis_id) references pwlhseis(pwlhseis_id);