Question

我正在使用MySQL，我有两个表格表格：

mysql> describe ing_categories;
+-------------+------------------+------+-----+---------+----------------+
| Field       | Type             | Null | Key | Default | Extra          |
+-------------+------------------+------+-----+---------+----------------+
| ID_Category | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| category    | varchar(64)      | NO   | UNI | NULL    |                |
+-------------+------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)

mysql> describe ing_titles;
+----------+------------------+------+-----+---------+----------------+
| Field    | Type             | Null | Key | Default | Extra          |
+----------+------------------+------+-----+---------+----------------+
| ID_Title | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| title    | varchar(128)     | NO   | UNI | NULL    |                |
+----------+------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)

我有第三个包含外键记录的表，外键是上面的表：

mysql> describe ing_title_categories;
+-------------------+------------------+------+-----+---------+----------------+
| Field             | Type             | Null | Key | Default | Extra          |
+-------------------+------------------+------+-----+---------+----------------+
| ID_Title_Category | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| ID_Title          | int(10) unsigned | NO   | MUL | NULL    |                |
| ID_Category       | int(10) unsigned | NO   | MUL | NULL    |                |
+-------------------+------------------+------+-----+---------+----------------+

如何创建ing_titles_categories表，以便外键的对是唯一的？

这是我的SQL语句：

CREATE TABLE ing_title_categories
(
    ID_Title_Category INTEGER UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
    ID_Title INTEGER UNSIGNED NOT NULL,
    ID_Category INTEGER UNSIGNED NOT NULL,
    FOREIGN KEY fk_title(ID_Title)
        REFERENCES ing_titles(ID_Title)
        ON UPDATE CASCADE
        ON DELETE RESTRICT,
    FOREIGN KEY fk_category(ID_Category)
        REFERENCES ing_categories(ID_Category)
        ON UPDATE CASCADE
        ON DELETE RESTRICT
) ENGINE=InnoDB;

我搜索了其他问题，他们涉及为外键制作索引;但我不想用外键索引，我希望约束为unique 对外键。

工具：
MySQL服务器版本：5.6.26

注意：

我不使用PHP，而是通过MySQL C ++ Connector使用C ++，所以请不要使用PHP 实例

创建唯一外键表

0 个答案: