Sql 客户已下订单的删除时触发

我正在为已删除的客户创建以前的客户表。 我想在从客户表中删除数据后创建一个触发器。 但是，我不希望所有客户都放在这个表中，只希望那些以前在系统中下过订单的客户。 我有两张桌子

Customer                 placed_order
Customer_Id              order_id
first_name               order_date
last_name                employee_ID
address                  fk1_customer_id

---

如何才能只插入在“已下订单”表中有记录的客户？

类似的情况如何

CREATE OR REPLACE TRIGGER CUSTOMER_AD
  AFTER DELETE ON CUSTOMER
  REFERENCING OLD AS OLD
  FOR EACH ROW
DECLARE
  nPlaced_order_count  NUMBER;
BEGIN
  SELECT COUNT(*)
    INTO nPlaced_order_count
    FROM PLACED_ORDERS p
    WHERE p.FK1_CUSTOMER_ID = :OLD.CUSTOMER_ID;

  IF nPlaced_order_count > 0 THEN
    INSERT INTO PREVIOUS_CUSTOMER(whatever, whatever, whatever)
      VALUES(whatever, whatever, whatever);
  END IF;

  -- Now clean up the PLACED_ORDERS table

  DELETE FROM PLACED_ORDERS p
    WHERE p.FK1_CUSTOMER_ID = :OLD.CUSTOMER_ID;
END CUSTOMER_AD;

将

任何内容

替换为适合您的

上一个客户

表的列名和值

CREATE OR REPLACE TRIGGER trg_customer_delete
BEFORE DELETE ON customer
FOR EACH ROW
REFERENCING new AS new old AS old
AS
  cnt INTEGER;
BEGIN
    SELECT COUNT(*)
      INTO cnt
      FROM placed_order
     WHERE fk_customer_id = :old.customer_id

    IF cnt > 0 THEN
        INSERT INTO previous_customer
        (customer_id, first_name, last_name, address)
        VALUES
        (:old.customer_id, :old.first_name, :old.last_name, :old.address);
    END IF;
END;
/

---

分享和享受。

像这样的东西怎么样

CREATE OR REPLACE TRIGGER CUSTOMER_AD
  AFTER DELETE ON CUSTOMER
  REFERENCING OLD AS OLD
  FOR EACH ROW
DECLARE
  nPlaced_order_count  NUMBER;
BEGIN
  SELECT COUNT(*)
    INTO nPlaced_order_count
    FROM PLACED_ORDERS p
    WHERE p.FK1_CUSTOMER_ID = :OLD.CUSTOMER_ID;

  IF nPlaced_order_count > 0 THEN
    INSERT INTO PREVIOUS_CUSTOMER(whatever, whatever, whatever)
      VALUES(whatever, whatever, whatever);
  END IF;

  -- Now clean up the PLACED_ORDERS table

  DELETE FROM PLACED_ORDERS p
    WHERE p.FK1_CUSTOMER_ID = :OLD.CUSTOMER_ID;
END CUSTOMER_AD;

将

任何内容

替换为适合您的

上一个客户

表的列名和值

CREATE OR REPLACE TRIGGER trg_customer_delete
BEFORE DELETE ON customer
FOR EACH ROW
REFERENCING new AS new old AS old
AS
  cnt INTEGER;
BEGIN
    SELECT COUNT(*)
      INTO cnt
      FROM placed_order
     WHERE fk_customer_id = :old.customer_id

    IF cnt > 0 THEN
        INSERT INTO previous_customer
        (customer_id, first_name, last_name, address)
        VALUES
        (:old.customer_id, :old.first_name, :old.last_name, :old.address);
    END IF;
END;
/

---

共享和享受。

首先，您必须在

下单

fk1.customer\u id

列上指定在删除时层叠的约束。只需更改该列上的外键约束

试试这个：

ALTER TABLE placed_order
MODIFY CONSTRAINT fk1_fk_customer_id
FOREIGN KEY (fk1_customer_id) REFERENCES customer(customer_id)
ON DELETE CASCADE;

接下来，您需要在客户上设置一个“删除前

”触发器，该触发器将对那些在
下单
表中有条目的客户进行审核

CREATE OR REPLACE TRIGGER trg_customer_delete
BEFORE DELETE ON customer
FOR EACH ROW
REFERENCING new AS new old AS old
AS
  cnt INTEGER;
BEGIN
    SELECT COUNT(*)
      INTO cnt
      FROM placed_order
     WHERE fk_customer_id = :old.customer_id

    IF cnt > 0 THEN
        INSERT INTO previous_customer
        (customer_id, first_name, last_name, address)
        VALUES
        (:old.customer_id, :old.first_name, :old.last_name, :old.address);
    END IF;
END;
/

首先，您必须在
placed\u order
fk1.customer\u id
列上指定要在删除时级联的约束。只需更改该列上的外键约束

试试这个：

ALTER TABLE placed_order
MODIFY CONSTRAINT fk1_fk_customer_id
FOREIGN KEY (fk1_customer_id) REFERENCES customer(customer_id)
ON DELETE CASCADE;

接下来，您需要在客户上设置一个“删除前
”触发器，该触发器将对那些在
下单
表中有条目的客户进行审核

CREATE OR REPLACE TRIGGER trg_customer_delete
BEFORE DELETE ON customer
FOR EACH ROW
REFERENCING new AS new old AS old
AS
  cnt INTEGER;
BEGIN
    SELECT COUNT(*)
      INTO cnt
      FROM placed_order
     WHERE fk_customer_id = :old.customer_id

    IF cnt > 0 THEN
        INSERT INTO previous_customer
        (customer_id, first_name, last_name, address)
        VALUES
        (:old.customer_id, :old.first_name, :old.last_name, :old.address);
    END IF;
END;
/

您想如何处理
placed\u order
表中的记录？它们应该被删除还是设置为null？嗯，好的，它们也会从数据库中删除。我有一个正在运行的过程，它当前会从我使用的两个表中删除。你真的不需要一个过程来完成这项工作。只要一个外键在DELETE CASCADE上带有
，
就可以了。嗨，是的，我知道，但是我已经有一个程序在运行，所以我们可以使用它，你知道触发器是什么吗？你想对
下订单的
表中的记录做什么？它们应该被删除还是设置为null？嗯，好的，它们也会从数据库中删除。我有一个正在运行的过程，它当前会从我使用的两个表中删除。你真的不需要一个过程来完成这项工作。只要一个外键，在DELETE CASCADE上加上
，
就可以了。嗨，是的，我知道，但我已经有一个程序在运行，所以不妨使用它，你对触发器有什么想法吗？这看起来很完美，只需要一个问题：引用“老如旧”意味着什么？@RichardClare-这意味着什么“在执行删除之前引用值时使用旧名称”。我可以说类似于
将旧名称引用为O
，然后使用，例如
：O.CUSTOMER\u ID
（感谢您的更正/添加冒号，@AlexPoole）.这似乎很完美，只有一个问题：引用old as old意味着什么？@RichardClare-它的意思是“在引用值时使用old的名称，就像执行删除之前一样”。我可以说类似于
引用old as O
，然后使用，例如
：O.CUSTOMER\u ID
（感谢您的更正/添加冒号，@AlexPoole）。