數據庫-Mysql創建表的時候創建不了外鍵

Mysql創建表的時候創建不了外鍵

create table orderdetail
(
id int UNSIGNED AUTO_INCREMENT PRIMARY KEY,
oid varchar(20) ,
fname varchar(20) ,
fprice decimal(5,2),
num SMALLINT UNSIGNED not null,
subtotals decimal(5,2) not null,
CONSTRAINT fk_orderdetail_oid FOREIGN KEY (oid) REFERENCES orders (oid),
CONSTRAINT fk_orderdetail_fname FOREIGN KEY (fname) REFERENCES fruit (fname),
CONSTRAINT fk_orderdetail_fprice FOREIGN KEY (fprice) REFERENCES fruit (fprice)
);
顯示錯誤信息是
[Err] 1215 - Cannot add foreign key constraint

求問大神出錯了在哪呢這語法！！在線等！！

最佳回答：

（1）外鍵對應的字段數據類型不一致

（2）兩張表的存儲引擎不一致

（3）設置外鍵時“刪除時”設置為“SET NULL”