Sqlite 外键不匹配？

Question

我已阅读 this 问题并理解引用的外键是唯一的，但不知何故插入 table 仍然抛出外键不匹配错误：

CREATE TABLE medication (
med_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
med_name VARCHAR (20) NOT NULL, 
dosage VARCHAR (10)
);    

CREATE TABLE disease (
dis_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
disease_name VARCHAR (20) NOT NULL
);    

CREATE TABLE dis_med (
disease_id int NOT NULL, 
medication_id int NOT NULL, 
CONSTRAINT PK_dis_med PRIMARY KEY (disease_id, medication_id), 
CONSTRAINT FK_dis FOREIGN KEY (disease_id) REFERENCES disease (dis_id), 
CONSTRAINT FK_med FOREIGN KEY (medication_id) REFERENCES medication (med_id));

CREATE TABLE user_disease (
user_id REFERENCES user (user_id), 
dis_id REFERENCES disease (dis_id), 
med_id REFERENCES dis_med(medication_id),
CONSTRAINT PK_dis_user PRIMARY KEY (user_id, dis_id)
);

通过我引用问题中的列表：

parent table（药物、疾病）存在。
parent 列存在
child table 引用了 parent table

更新1
我能够通过复合外键更改 user_disease table 来插入数据并绕过错误。如果有人能指出这里最好的设计是什么，我将不胜感激。非常感谢！

CREATE TABLE user_disease (
user_id REFERENCES user (user_id), 
dis_id REFERENCES disease (dis_id), 
med_id REFERENCES dis_med(medication_id),
CONSTRAINT FK_dis_med FOREIGN KEY REFERENCES dis_med(disease_id, medication_id),
CONSTRAINT PK_dis_user PRIMARY KEY (user_id, dis_id)
);

Answer 1

来自 SQLite Foreign Key Support/3. Required and Suggested Database Indexes:

Usually, the parent key of a foreign key constraint is the primary key of the parent table.
If they are not the primary key, then the parent key columns must be collectively subject to a UNIQUE constraint or have a UNIQUE index.

有了这个：

CREATE TABLE user_disease (
...........................
med_id REFERENCES dis_med(medication_id),
...........................
);

user_disease 的 med_id 列引用了 dis_med 的 medication_id 列，它不是 dis_med 的 PRIMARY KEY 并且那里对它没有 UNIQUE 约束。它只是引用 med_id of medication .

为什么需要 user_disease 中的 med_id 列？
您有 dis_id 引用 disease，它也可用于从 dis_med（所有）检索来自 dis_med 的该疾病的行。

Sqlite 外键不匹配？

Sqlite foreign key mismatch?

sqlite

entity-relationship

foreign-keys