Oracle：错误 ORA-02270（此列列表没有匹配的唯一键或主键）

Question

我尝试创建 4 个表并将它们 link 放在一起，但它显示此错误 ORA-02270。我怎样才能解决这个问题？我在声明导致此错误的外键和主键时是否有任何错误。

CREATE table City (
    city_name VARCHAR(128),
    state_name VARCHAR(128),
    population number,
    elevation number,
    PRIMARY KEY (city_name, state_name),
    FOREIGN KEY (city_name) REFERENCES Mayor(city_name)
);

CREATE table State (
    state_name VARCHAR(128) PRIMARY KEY,
    region VARCHAR(128),
    FOREIGN KEY (state_name) REFERENCES City(state_name),
    FOREIGN KEY (state_name) REFERENCES Mayor(state_name),
    FOREIGN KEY (state_name) REFERENCES Governor(state_name)
);

CREATE table Mayor (
    mayor_name VARCHAR(128),
    city_name VARCHAR(128),
    state_name VARCHAR(128),
    party VARCHAR(128),
    PRIMARY KEY (mayor_name, city_name, state_name)
);

CREATE table Governor (
    governor_name VARCHAR(128),
    state_name VARCHAR(128),
    party VARCHAR(128),
    PRIMARY KEY (governor_name, state_name)
);

Answer 1

你的外键都搞错了，导致语法无效的关系。我理解的关系如下：

一位州长提到了一个州
一个城市代表一个州
一位市长提到了一座城市

可能，您还应该有一个 region table，state table 会引用它。

这是一个有效的并实现了上述关系的新版本：

CREATE table State (
    state_name VARCHAR(128) PRIMARY KEY,
    region VARCHAR(128)
);

CREATE table Governor (
    governor_name VARCHAR(128),
    state_name VARCHAR(128),
    party VARCHAR(128),
    PRIMARY KEY (governor_name, state_name),
    FOREIGN KEY (state_name) REFERENCES State(state_name)
);

CREATE table City (
    city_name VARCHAR(128),
    state_name VARCHAR(128),
    population number,
    elevation number,
    PRIMARY KEY (city_name, state_name),
    FOREIGN KEY (state_name) REFERENCES State(state_name)
);


CREATE table Mayor (
    mayor_name VARCHAR(128),
    city_name VARCHAR(128),
    state_name VARCHAR(128),
    party VARCHAR(128),
    PRIMARY KEY (mayor_name, city_name, state_name),
    FOREIGN KEY (state_name, city_name) REFERENCES City(state_name, city_name)
);

Demo on DB Fiddle.

Oracle：错误 ORA-02270（此列列表没有匹配的唯一键或主键）

Oracle: Error ORA-02270 (no matching unique or primary key for this column-list)

sql

database

oracle

foreign-keys

create-table