没有主键的外键可供参考 [英] Foreign Key with NO primary key to refer
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问题描述
我有以下两个表.
CREATE TABLE parent
( c1 INTEGER );
CREATE TABLE child
(
c1 INTEGER,
c2 INTEGER,
c3 INTEGER,
CONSTRAINT fk_c3 FOREIGN KEY(c3) REFERENCES parent(c1)
);
您必须已经注意到c1
列不是Parent表中的主键.
不用以c1
作为主键,是否可以在子表中引用它?
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
是否可以在不将'c1'作为主键的情况下在子表中引用它?
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-不必是主键.您可以在该列上创建一个唯一的约束.
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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