1

我在数据库中创建了两个表，products 和 shopping_list。我已经为产品提供了一个外键参考 shopping_list，即 product.shopping_list_id。

我正在尝试在 ruby​​ on rails 中查找购物清单中存在的全部产品，但出现错误。

我给了一个文本框来输入值，该值作为总项目存储在数据库中。

但是当我在数据库中添加新产品时，数据库中的数量没有更新。

我的 shopping_list 表如下：-

CREATE TABLE shopping_lists
(
  id serial NOT NULL,
  shopping_list_name character varying(255),
  shopping_list_status character varying(255) DEFAULT 'OPEN'::character varying,
  total_items character varying(255) DEFAULT 0,
  created_at timestamp without time zone NOT NULL,
  updated_at timestamp without time zone NOT NULL,
  deleted integer NOT NULL DEFAULT 0,
  CONSTRAINT shopping_lists_pkey PRIMARY KEY (id)
)

我的产品表如下：-

CREATE TABLE products
(
  id serial NOT NULL,
  shopping_list_id integer NOT NULL,
  product_name character varying(255) DEFAULT 'null'::character varying,
  product_category character varying(255),
  quantity integer,
  status character varying(255) DEFAULT 'OPEN'::character varying,
  deleted integer NOT NULL DEFAULT 0,
  CONSTRAINT products_pkey PRIMARY KEY (id)
)

我的 Html 文档，即我在其中输入值的列表是这样的：-

<head>
  <%= javascript_include_tag :application %>
  <%= csrf_meta_tag %>
</head>
<% if @shopping_lists.blank? %>
  <p>There are no shopping_lists currently in the system.</p>
<% else %>
  <p>These are the shopping_lists in the system</p>
  <table border="1">
  <tr><td>shopping_list No.</td><td>shopping_list Name</td><td>status</td><td>quantity</td><td>Edit</td><td>Delete</td></tr>
  <% @shopping_lists.each do |c| %>
    <tr>
   <td><%= link_to c.id, {:action => 'get_product', :id => c.id} %> &nbsp;</td>
    <td><%= c.shopping_list_name %>&nbsp;</td>
    <td><%= c.shopping_list_status %>&nbsp;</td>
     <td><%= c.total_items %>&nbsp;</td>
    <td><%= link_to 'Edit', {:action => 'edit', :id => c.id} %> &nbsp;</td>
    <td><%= link_to 'Delete', {:action => 'delete', :id => c.id},
    :data => { :confirm => "Are you sure you want to delete this shopping_list?" } %></td>
    </tr>
  <% end %>
  </table>
<% end %>
<p><%= link_to "Add new shopping_list", {:action => 'new' }%></p>

简而言之，我想实现以下查询：-

Select count(*) from products where shopping_list_id = '';

你能帮我么

4

1 回答 1

3

如果你真的想要这个：

Select count(*) from products where shopping_list_id = '';

你可以做：

Product.count(:conditions => "shopping_list_id is NULL")
于 2013-02-25T13:19:10.893 回答