Error while implementing count in Rails 3.2

Question

I have created two tables in the database, products and shopping_list. I have given products a foreign key reference of shopping_list which is product.shopping_list_id.

I am trying to find the total products present in the shopping list in ruby on rails but I am getting an error.

I have given a text box to enter the value,and that value is stored in the database as total items.

But when I add new products in the database the quantity is not getting updated in the database.

My shopping_list table is as follows:-

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)
)

My product table is as follows:-

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)
)

My Html document ie list in which I enter my value is this:-

<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>

In short I want to implement the following query:-

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

Can you please help me

Kaeros · Accepted Answer · 2013-02-25 13:19:10Z

3

If you really want this:

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

You can do:

Product.count(:conditions => "shopping_list_id is NULL")

answered Feb 25, 2013 at 13:19

Kaeros

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8 Comments

deefour Over a year ago

Using .size is better; if the Product collection already exists, it won't run a 2nd query against the database.

Rockking Over a year ago

@ kaeros I wat to implement this in shopping list.so can you tell me where to make the changes

Kaeros Over a year ago

@Deefour Updated my answer, i think this reads better. What do you think?

Kaeros Over a year ago

@ArseneW @shopping_list.products.size In your case it is c.products.size

Rockking Over a year ago

Where do I put this @Kaeros

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