Question

create  table product 
(productid varchar(10) primary key,
productname varhchar(10),
totalquantity number(10),
reorderlevel number(10),
remainingquatity number(10) );


1. produtid       productname  totalquantity  reorderlevel remainingquantity

      0001           abc               100         0                0

      0002            xyz               80         0                0

create table orders 
(orderno varchar(10),
productid(10) references  product(productid),
quantityordered number(10));

现在我的问题是，无论何时发出订单，remainingquantity

，我都需要对reorderlevel和product table进行自动更新

我尝试了触发器，但是它无法正常工作请帮助我，如果还有其他概念而不是触发器可以用来执行此过程请提及

Answer 1

此触发器应该有效

   create or replace trigger product_update
      BEFORE insert on orders
      for each row
    begin

        UPDATE PRODUCT
           SET remainingquantity = totalquantity - :new.quantityordered,
               reorderlevel = remainingquantity - :new.quantityordered
         WHERE PRODUCT_ID = :new.PRODUCT_ID;  

    end;

Answer 2

或者您可以规范化表格（为Oracle 11g重新编译）：

并在查询中使用join

CREATE TABLE product(
  id NUMBER(15,0) NOT NULL CONSTRAINT pk_product PRIMARY KEY, 
  name VARCHAR2(100), 
  totalquantity NUMBER(15,0)
)/

CREATE TABLE orders(
  id NUMBER(15,0) NOT NULL CONSTRAINT pk_orders PRIMARY KEY,
  orderno VARCHAR2(100),
  quantityordered NUMBER(15,0),
  productid NUMBER(15,0) CONSTRAINT fk_orders_product_id REFERENCES product(id)
)/

测试数据：

select Q.id, Q.name, 
  Q.totalquantity - Q.orderdquantity as remainingquantity,
  Q.totalquantity - 2*Q.orderdquantity as reorderlevel
from
  (select p.id, p.name, p.totalquantity, 
     coalesce(sum(o.quantityordered) ,0) as orderdquantity
   from product p
   left join orders o on o.productid = p.id
   group by p.id, p.name, p.totalquantity) Q

结果：

insert into product(id, name, totalquantity) values(1, 'apple', 100)/
insert into product(id, name, totalquantity) values(2, 'tomato', 100)/
insert into product(id, name, totalquantity) values(3, 'carrot', 100)/

insert into orders(id, orderno, quantityordered, productid) values(1, '№1', 10, 1)/
insert into orders(id, orderno, quantityordered, productid) values(2, '№2', 3, 1)/
insert into orders(id, orderno, quantityordered, productid) values(3, '№3', 23, 2)/

Proof SQLFiddle

如何通过减去其他表的两列来更新表的列

2 个答案: