Database 删除过程无法运行并出现错误？

我创建了一个过程来删除三个表中的数据，这些表都是用外键链接的，但没有运行。程序如下

PROCEDURE remove_customer (customer_id VARCHAR2) IS
BEGIN
DELETE FROM order_line
WHERE  order_line.order_id = placed_order.order_id;
DELETE FROM placed_order
WHERE placed_order.customer_id = customer.customer_id;
DELETE FROM customer
WHERE customer.customer_id = remove_customer.customer_id;
total_customers := total_customers - 1;
END;

这是三张桌子的结构。有人知道我为什么会出错吗

customer(
    Customer_ID INTEGER NOT NULL,
    Country VARCHAR(15),
    First_Name  VARCHAR(30),
    Last_Name   VARCHAR(30),
    CONSTRAINT  pk_customer PRIMARY KEY (Customer_ID)
);


    placed_order(
    order_id    INTEGER NOT NULL,
    order_date  VARCHAR(15),
    fk1_Customer_ID INTEGER NOT NULL,
    fk2_Employee_ID INTEGER NOT NULL,
    fk3_order_type_id   INTEGER NOT NULL,
    CONSTRAINT  pk_placed_order PRIMARY KEY (order_id)
);


    order_line(
    order_line_id   INTEGER NOT NULL,
    fk1_order_id    INTEGER NOT NULL,
    fk2_product_id  INTEGER NOT NUL,
    CONSTRAINT  pk_order_line PRIMARY KEY (order_line_id)
);

下面是它抛出的两个错误

ORA-00904:“已下订单”。“订单ID”：无效标识符编译失败，第30行

---

ORA-00904：“客户”。“客户ID”：无效标识编译失败，第32行您不能仅在DELETE语句中引用其他表中的列。每个语句都需要从参数值customer_id开始。这应该满足您的要求：

PROCEDURE remove_customer (customer_id VARCHAR2) IS
BEGIN

  DELETE FROM order_line
  WHERE  order_line.order_id in
  ( SELECT order_id FROM placed_order
    WHERE placed_order.customer_id = remove_customer.customer_id
  );

  DELETE FROM placed_order
  WHERE placed_order.customer_id = remove_customer.customer_id;

  DELETE FROM customer
  WHERE customer.customer_id = remove_customer.customer_id;

  total_customers := total_customers - 1;

END;

---

您好，谢谢，这很有意义，有一件事我得到一个SQL命令没有正确结束，是它缺少一个“；”在第一次删除中？嗯，当它没有；它只是有那个错误，现在我已经添加了它，它给我负载或错误？ORA-00904:“订单行”。“订单ID”：无效标识符编译失败PLS-00302:组件“客户ID”必须声明编译失败PL/SQL:ORA-00904:“已下订单”。“客户ID”：无效标识符编译失败任何想法？您必须确保在语句中使用的列名与实际列名匹配-例如

order\u line。order\u id

应为

order\u line。根据表定义，fk1\u order\u id

。如果您还没有，我建议您在表中定义真正的外键。H，是的，已经定义了，但感谢您的提醒