MySQL中文参考手册 - 常用查询的例子

3.5 使用外键

不需要外键联结2个表。

MySQL唯一不做的事情是CHECK以保证你使用的键确实在你正在引用表中存在，并且它不自动从有一个外键定义的表中删除行。如果你象平常那样使用你的键值，它将工作得很好！

CREATE TABLE persons (
id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
name CHAR(60) NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE shirts (
id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
style ENUM('t-shirt', 'polo', 'dress') NOT NULL,
color ENUM('red', 'blue', 'orange', 'white', 'black') NOT NULL,
owner SMALLINT UNSIGNED NOT NULL REFERENCES persons,
PRIMARY KEY (id)
);
INSERT INTO persons VALUES (NULL, 'Antonio Paz');
INSERT INTO shirts VALUES
(NULL, 'polo', 'blue', LAST_INSERT_ID()),
(NULL, 'dress', 'white', LAST_INSERT_ID()),
(NULL, 't-shirt', 'blue', LAST_INSERT_ID());
INSERT INTO persons VALUES (NULL, 'Lilliana Angelovska');
INSERT INTO shirts VALUES
(NULL, 'dress', 'orange', LAST_INSERT_ID()),
(NULL, 'polo', 'red', LAST_INSERT_ID()),
(NULL, 'dress', 'blue', LAST_INSERT_ID()),
(NULL, 't-shirt', 'white', LAST_INSERT_ID());
SELECT * FROM persons;
+----+---------------------+
| id | name　　　　　　　　|
+----+---------------------+
|　1 | Antonio Paz　　　　 |
|　2 | Lilliana Angelovska |
+----+---------------------+
SELECT * FROM shirts;
+----+---------+--------+-------+
| id | style　 | color　| owner |
+----+---------+--------+-------+
|　1 | polo　　| blue　 |　　 1 |
|　2 | dress　 | white　|　　 1 |
|　3 | t-shirt | blue　 |　　 1 |
|　4 | dress　 | orange |　　 2 |
|　5 | polo　　| red　　|　　 2 |
|　6 | dress　 | blue　 |　　 2 |
|　7 | t-shirt | white　|　　 2 |
+----+---------+--------+-------+
SELECT s.* FROM persons p, shirts s
WHERE p.name LIKE 'Lilliana%'
AND s.owner = p.id
AND s.color <> 'white';
+----+-------+--------+-------+
| id | style | color　| owner |
+----+-------+--------+-------+
|　4 | dress | orange |　　 2 |
|　5 | polo　| red　　|　　 2 |
|　6 | dress | blue　 |　　 2 |
+----+-------+--------+-------+