我试图创建一个约束父表中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。