Question

我已经在MySQL中创建了一个表！并尝试了一些查询来改变表并向表中添加外键！但它们都不起作用？没有任何错误消息，但没有任何事情发生......

我需要确切的查询才有效！ :(

详细说明：

表1：用户列： id
表2： Pokemon_ref 栏目： pkmn_id

如果在表1中完成插入，那么它也应该在表2中添加！

Answer 1

    category INT NOT NULL, id INT NOT NULL,
    price DECIMAL,
    PRIMARY KEY(category, id)
)   ENGINE=INNODB;

CREATE TABLE customer (
    id INT NOT NULL,
    PRIMARY KEY (id)
)   ENGINE=INNODB;

CREATE TABLE product_order (
    no INT NOT NULL AUTO_INCREMENT,
    product_category INT NOT NULL,
    product_id INT NOT NULL,
    customer_id INT NOT NULL,

    PRIMARY KEY(no),
    INDEX (product_category, product_id),
    INDEX (customer_id),

    FOREIGN KEY (product_category, product_id)
      REFERENCES product(category, id)
      ON UPDATE CASCADE ON DELETE RESTRICT,

    FOREIGN KEY (customer_id)
      REFERENCES customer(id)
)

Answer 2

样品：

ALTER TABLE tablename
ADD CONSTRAINT FK_Name_ID FOREIGN KEY (fk_ID)
    REFERENCES (R_id);

<强> https://dev.mysql.com/doc/refman/5.1/en/create-table-foreign-keys.html

<强> http://www.w3schools.com/sql/sql_foreignkey.asp

<强> Alter table to give foreign key constraint

表创建后的外键

2 个答案: