SQL 不允许向外键添加数据

Question

我运行在 MySQL 中出现错误，它不允许我输入外键数据。这是我的数据：

 create table Location(
LocationID char(4) primary key,
LocationName char(20),
LocationState char(3),
LocationPostCode char(4),
StartLoc char(3),
EndLoc char(3)
);
drop table Location;
insert into Location values ('L10','Norwood','TAS','7250','L31','L30');
insert into Location values ('L11','Cressy','TAS','7586','L33','L32');
insert into Location values ('L12','Launceston','TAS','7907','L35','L34');
insert into Location values ('L13','Epping Forest','TAS','7354','L37','L36');
insert into Location values ('L14','Avoca','TAS','7812','L39','L38');
insert into Location values ('L15','Royal George','TAS','7009','L41','L40');
insert into Location values ('L16','Westbury','TAS','7893','L43','L42');

create table TripSchedule(
ScheduleID char(3),
foreign key(StartLoc) references Location(StartLoc),
foreign key(EndLoc) references Location(EndLoc),
foreign key(RequestID) references BookingReq(RequestID),
foreign key(TruckVINNum) references Allocation(TruckVINNum),
foreign key(TransportID) references Allocation(TransportID),
foreign key(StaffID) references Staff(StaffID),
TripStart char(40),
TripEnd char(40)
);

drop table TripSchedule;
insert into TripSchedule values('S23',L11','L10', 'R101', 'VO20','T1','S1''6th of December 2020-1:30pm','7th of December 2021-1:30 pm');
insert into TripSchedule values('S24', 'L13','L12', 'R102', 'VO20','T1','S1','6th of December 2020-1:30pm','7th of December, 2021-1:30 pm');
insert into TripSchedule values('S25', 'L15','L14', 'R103', 'VO20','T1','S1','6th of December 2020-1:30pm','7th of December, 2021-1:30 pm');
insert into TripSchedule values('S26', 'L17','L16', 'R104', 'VO20','T1','S1','6th of December 2020-1:30pm','7th of December, 2021-1:30 pm');
insert into TripSchedule values('S27', 'L19','L18', 'R105', 'VO20','T1','S1','6th of December 2020-1:30pm','7th of December, 2021-1:30 pm');
insert into TripSchedule values('S28', 'L21','L20', 'R101', 'VO20','T1','S1','6th of December 2020-1:30pm','7th of December, 2021-1:30 pm');
insert into TripSchedule values('S29', 'L23','L22', 'R106', 'VO20','T1','S1','6th of December 2020-1:30pm','7th of December, 2021-1:30 pm');

我遇到的问题有点奇怪，它与 Location 和 TripSchedule 之间的关系有关 table。 SQL 将允许输入 TripSchedule table 的插入值的前三行，但是插入值的其余部分给出错误：“错误代码：1452。无法添加或更新子行: 外键约束失败 (assessment.tripschedule, CONSTRAINT tripschedule_ibfk_1 FOREIGN KEY (StartLoc) REFERENCES location (LocationID)).

我尝试将 StartLoc 和 EndLoc 引用为位置 table 中的主键，并且还尝试从位置 table 中完全删除 StartLoc 和 EndLoc，但仍然遇到同样的问题。有什么解决办法吗？

Answer 1

您的外键约束要求位置存在才能将它们指定为 StartLoc。您的第四到第七个插入将 StartLoc 指定为 L17、L19、L21 和 L23，其中 none 是存在的 LocationID。

要么在插入引用它们的 TripSchedule 记录之前创建位置记录，要么删除您的外键约束：

alter table TripSchedule drop constraint tripschedule_ibfk_1;

SQL 不允许向外键添加数据

SQL not allowing to add data into foreign keys

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