外键“fk_orders_SalesRep”在引用表“orders”中引用了无效的列“snum”

Question

我做错了什么？我正在尝试将外键添加到现有表中

ALTER TABLE orders 
ADD CONSTRAINT fk_orders_SalesRep
                  FOREIGN KEY (snum) 
                  REFERENCES SalesRep(snum);

表信息

create table SalesRep(
    snum varchar(5) primary key,
    sname varchar(10),
    hours Int 
)

create table orders(
    odId varchar(5) primary key,
    itId varchar(5) foreign key(itId) references items(itId)
)

Answer 1

就像Martin说的，先添加这一列

ALTER TABLE orders
ADD snum varchar(5);

然后添加fk

ALTER TABLE orders 
ADD CONSTRAINT fk_orders_SalesRep
                  FOREIGN KEY (snum) 
                  REFERENCES SalesRep(snum);