没有主键的外键引用 [英] Foreign Key with NO primary key to refer

问题描述

我有以下两张表.

CREATE TABLE parent
( c1 INTEGER );

CREATE TABLE child
(
 c1 INTEGER,
 c2 INTEGER,
 c3 INTEGER,
 CONSTRAINT fk_c3 FOREIGN KEY(c3) REFERENCES parent(c1)
);

您一定已经注意到列 c1 不是父表中的主键.有没有办法在子表中引用它而不将 c1 作为主键?

You must have noticed that column c1 is NOT a primary key in Parent table. Is there any way to refer it in Child table without making c1 as a primary key?

推荐答案

有没有办法在子表中引用它而不将'c1'作为主键?

Is there any way to refer it in Child table without making 'c1' as a primary key?

是的.外键只需要引用唯一约束 - 它不必是主键.您可以在该列上创建一个独特的约束.

Yes. A foreign key needs only to refer to a unique constraint - it does not have to be a primary key. You could create a unique contraint on that column.

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