尝试在sql中创建外键时出现错误？

Question

CREATE TABLE间（ RoomID为nvarchar（8）PRIMARY KEY， 容量数字（3）

）

CREATE TABLE RoomType（ RoomType nvarchar的（2）主键， 描述为nvarchar（20）， 责任管理为nvarchar（20） ）

ALTER TABLE房

附加约束fk_type外键（类型）引用室类型（Type）

主要错误0x80040E11，次要错误0

ALTER TABLE房 附加约束fk_type外键（类型）引用RoomType（类型） 无效的列ID。 [类型]

Answer 1

您可以创建结合RoomID和EquipmentType像这样的表RoomEquipment：

create table RoomEquipment (
    RoomID int, 
    EquipmentType nvarchar(1), 
    primary key (roomid, equipmenttype), 
    constraint fk_roomequipment_equipment_type 
      foreign key (equipmenttype) 
      references equipment(equipmenttype), 
    constraint fk_roomequipment_equipment_roomid 
      foreign key (roomid) 
      references room(roomid) 
); 

其它表可能是这样的：

-- I prefer using char datatype for predictable number of characters in a field 
CREATE TABLE RoomType (
Roomtype nvarchar(2) NOT NULL, 
Description nvarchar(20), 
Responsibility nvarchar(20), 
primary key (Roomtype) 
); 

-- You could use char(1) instead of nvarchar(1) for type; I'd prefer using int instead 
create table Equipment (
Equipmenttype nvarchar(1) NOT NULL, 
Description nvarchar(10) 
); 

-- Added a unique key to assist with good foreign key relationship 
alter table Equipment add constraint uk_equipment_equipmenttype unique (equipmenttype); 

-- Just use an int or char if roomID length is predictable 
Create table Room (
RoomID nvarchar(8), 
Capacity numeric(3), 
Roomtype(fk,nvarchar(2) 
); 

alter table room add constraint uk_room_id unique (roomid); 

例子是在这里：http://sqlfiddle.com/#!3/f510b