Question

我使用以下查询将外键添加到我的表中：

$query = "ALTER TABLE reserved ADD CONSTRAINT fk_test FOREIGN KEY (personel_num) REFERENCES members (personel_num) ON DELETE CASCADE ON UPDATE;";
if ($conn->query($query) === TRUE) {
    return true;
} else {
    echo $conn->error;
}

但我收到以下错误：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1

表personel_num中的

members是主键。

Answer 1

试试这个

    $query = "ALTER TABLE reserved ADD CONSTRAINT fk_test FOREIGN KEY (personel_num)
 REFERENCES members members (personel_num) ON DELETE CASCADE ON UPDATE NO ACTION;";

Answer 2

;不是SQL语法的一部分，它只是一些工具用来表示SQL语句结束位置的终结符。由于您以编程方式将SQL语句发送到数据库，因此不需要它。

此外，您应在更新时指定NO ACTION：

$query = "ALTER TABLE reserved ADD CONSTRAINT fk_test " .
         "FOREIGN KEY (personel_num) REFERENCES members (personel_num) " .
         "ON DELETE CASCADE ON UPDATE NO ACTION";

MySQL - 添加外键时出错

2 个答案: