无法添加外键约束,让我发疯,请帮忙:)

Question

CREATE TABLE country
(
country_id VARCHAR (20),
country_name CHAR (20),
state_no INT (5),
PRIMARY KEY (country_id));

CREATE TABLE cities
(
city_name VARCHAR (20),
country_name CHAR (20),
country_id VARCHAR (20),
PRIMARY KEY (city_name),
FOREIGN KEY (country_id) REFERENCES country);

这是我创建的两个表,第一个是执行正常但我得到1215错误无法添加外键约束.我真的不确定为什么并且已经把头发拉了近一个小时.我确信这很简单,我很蠢.

Answer 1

您必须指定要引用的列.

FOREIGN KEY (country_id) REFERENCES country(country_id));