mysql - 尝试将多个外键添加到单个表时出错

Question

我正在尝试创建一个约束来自父表的 3 个外键的子表，但收到错误1215:无法添加外键约束

父表:

    CREATE TABLE `Availability` (
   `time_of_day` varchar(20) NOT NULL,
   `day_of_week` varchar(20) NOT NULL,
   `email` varchar(60) NOT NULL,
   PRIMARY KEY (`time_of_day`,`day_of_week`,`email`),
   KEY `email` (`email`),
   CONSTRAINT `Availability_ibfk_1` FOREIGN KEY (`email`) REFERENCES `service_provider` (`email_service_provider`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8

子表(由于上述错误我无法构建):

CREATE TABLE TEST1
(
  num_request INT NOT NULL,
  time_of_day VARCHAR(20) NOT NULL,
  day_of_week VARCHAR(20) NOT NULL,
  email VARCHAR(60) NOT NULL,
    PRIMARY KEY (num_request),
    Foreign key (time_of_day) references Availability(time_of_day),
    Foreign key (day_of_week) references Availability(day_of_week),
    Foreign key (email) references Availability(email)
  );

请告诉我我做错了什么......谢谢大家。

Answer 1

当您为具有复合主键(即多列的键)的表创建外键时，您也应该创建复合外键。

CREATE TABLE TEST1
(
  num_request INT NOT NULL,
  time_of_day VARCHAR(20) NOT NULL,
  day_of_week VARCHAR(20) NOT NULL,
  email VARCHAR(60) NOT NULL,
    PRIMARY KEY (num_request),
    Foreign key (time_of_day, day_of_week, email) references Availability(time_of_day, day_of_week, email)
)

外键的列应与其引用的主键或唯一键的列相匹配。它们应该具有相同的列数和相同的顺序。

您尝试做的是创建三个单独的约束，每个约束各一列。