我的带光标的购物车程序抛出错误答案

【问题标题】：My shopping cart procedure with cursor is throwing errors我的带光标的购物车程序抛出错误
【发布时间】：2019-09-19 16:55:51
【问题描述】：

我有一个小组项目，我们正在其中创建一个购物车应用程序。我得到了一些反馈并修复了它，把它变成了一个带有光标的过程。但是，我们仍然遇到我不知道如何修复的错误，例如尝试将空值放入不能为空的表列中。我不知道为什么它认为我正在尝试输入空值。我们的项目明天到期，所以请帮忙！

一开始我尝试将它作为触发器，但它不起作用，因此建议将其转换为带光标的过程，所以我这样做了。

create or replace PROCEDURE CANCELCART (arg_cart_id IN number)

IS
ws_prod_id number;
ws_item_quantity_in_cart number;
ws_cart_id number;
ws_cart_status char;

cursor cancel IS
select item_product_id, item_quantity_in_cart
FROM sc_items i
WHERE item_cart_id = arg_cart_id
group by item_product_id;

alreadycancelled exception;

BEGIN
select max(cart_id) into ws_cart_id
from sc_cart
where arg_cart_id = cart_id;

/*cart check*/
select max(cart_status) into ws_cart_status
from sc_cart
where arg_cart_id = cart_id;

if ws_cart_id is null
    then raise alreadycancelled;
    end if;

open cancel;
LOOP
fetch cancel into ws_prod_id, ws_item_quantity_in_cart;
    UPDATE sc_product p SET prod_quan_avail = prod_quan_avail + ws_quantity_in_cart, 
    prod_quan_sold = prod_quan_sold - ws_quantity_in_cart
    WHERE prod_id = ws_prod_id;
    DELETE FROM sc_items i WHERE i.item_cart_id = arg_cart_id;
END LOOP;
close cancel;

DELETE FROM sc_cart c WHERE c.cart_id = arg_cart_id;

EXCEPTION
when alreadycancelled 
    then raise_application_error(-20400, 'Cart does not exist');

END;

我需要此代码来取消购物车并将所有商品数量退回原始库存。

【问题讨论】：

标签： oracle stored-procedures plsql cursor oracle-apex

【解决方案1】：

除了使用数据类型定义 ws_quantity_in_cart 变量，并为其他类型的异常添加更多处理之外，您的代码块没有太多缺失的部分 (ORA-20400)

CREATE OR REPLACE PROCEDURE CANCELCART( arg_cart_id sc_cart.cart_id%type ) IS
    ws_prod_id               sc_product.prod_id%type;
    ws_item_quantity_in_cart sc_product.prod_quan_avail%type;
    ws_cart_id               sc_cart.cart_id%type;
    ws_cart_status           sc_cart.cart_status%type;
    ws_quantity_in_cart      sc_product.prod_quan_sold%type;

    cursor cancel IS
    select item_product_id, item_quantity_in_cart
      from sc_items i
     where item_cart_id = arg_cart_id
     group by item_product_id;

    alreadycancelled exception;

BEGIN
    select max(cart_id)
      into ws_cart_id
      from sc_cart
     where arg_cart_id = cart_id;

    /*cart check*/
    select max(cart_status)
      into ws_cart_status
      from sc_cart
     where arg_cart_id = cart_id;

    if ws_cart_id is null
        then raise alreadycancelled;
        end if;

    open cancel;
    loop
    fetch cancel into ws_prod_id, ws_item_quantity_in_cart;
        update sc_product p 
           set prod_quan_avail = prod_quan_avail + ws_quantity_in_cart,
               prod_quan_sold = prod_quan_sold - ws_quantity_in_cart
         where prod_id = ws_prod_id;
        delete sc_items i where i.item_cart_id = arg_cart_id;
    end loop;
    close cancel;

    delete sc_cart c where c.cart_id = arg_cart_id;

 exception when alreadycancelled  then raise_application_error(-20400, 'Cart does not exist');
           when      others       then raise_application_error(SQLCODE,SQLERRM);

END;

优先使用<table_name>.<column_name>.%type列的原始数据类型来定义变量的数据类型，不要使用char类型的定长字符串类型变量，改用varchar2。

【讨论】：