Question

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，我不希望所有客户只在此表中放置那些之前已在系统中下订单的客户。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

如何只插入在已下订单表中有记录的客户？

Answer 1

像

这样的东西

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whatever替换为适合您的PREVIOUS_CUSTOMER表的列名和值。

分享并享受。

Answer 2

首先，您必须在placed_order。fk1.customer_id列上指定要在删除时级联的约束。只需更改该列的外键约束即可。

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，客户需要BEFORE DELETE触发器，以便对那些在placed_order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;
/

触发删除客户订单的位置

2 个答案: