MySQL:使用两个外键创建表失败,出现"Duplicate key name"错误

Question

在尝试创建新表时,MySQL正在给我一个我无法解释的错误.

CREATE TABLE Products (
    id INT NOT NULL,
    PRIMARY KEY(id)
);

CREATE TABLE WarehouseMovements (
    time        DATETIME           NOT NULL,
    product1    INT                NOT NULL,
    product2    INT                NOT NULL,

    FOREIGN KEY WarehouseMovements(product1) REFERENCES Products(id),
    FOREIGN KEY WarehouseMovements(product2) REFERENCES Products(id)
);

这失败了ERROR 1061 (42000): Duplicate key name 'WarehouseMovements'.如果我删除外键约束成功,但我想确保product1和product2实际上指向某个地方.

默认引擎是InnoDB.

查询有什么问题？

Answer 1

尝试使FK名称不同:

CREATE TABLE Products (
    id INT NOT NULL,
    PRIMARY KEY(id)
);

CREATE TABLE WarehouseMovements (
    time        DATETIME           NOT NULL,
    product1    INT                NOT NULL,
    product2    INT                NOT NULL,

    FOREIGN KEY IX_WarehouseMovements_product1(product1) REFERENCES Products(id),
    FOREIGN KEY IX_WarehouseMovements_product2(product2) REFERENCES Products(id)
);

UPDATE

这是索引或FK名称,而不是表名.请参阅create-table-foreign-keys文档:

[CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (index_col_name, ...)
REFERENCES tbl_name (index_col_name,...)

哪个说

index_name表示外键ID.如果给定,则在显式定义外键的索引时忽略该值.否则,如果MySQL为外键创建索引,则它将index_name用于索引名称.

Answer 2

您必须向 FK 添加具有不同名称的约束

CREATE TABLE Products (
    id INT NOT NULL,
    PRIMARY KEY (id)
);

CREATE TABLE WarehouseMovements (
    time DATETIME NOT NULL,
    product1 INT NOT NULL,
    product2 INT NOT NULL,
    CONSTRAINT fk_product_1 FOREIGN KEY (product1) REFERENCES Products (id),
    CONSTRAINT fk_product_2 FOREIGN KEY (product2) REFERENCES Products (id)
);