title: show items that has no match in the DBtable as item_name = 0
body: <p>These are my tables in my database. </p>
  
  <pre><code>order_items
  +---------------+-------------------+----------------+---------------+
  |   order_id    |     datesales     |       qty      |    product_id |
  +---------------+-------------------+----------------+---------------+
  |     1         |      timestamp    |        5       |      1        |
  |     1         |      timestamp    |        10      |      2        |
  |     1         |      timestamp    |        10      |      3        |
  |     1         |      timestamp    |        10      |      4        |
  |     2         |      timestamp    |        5       |      1        |
  |     2         |      timestamp    |        10      |      2        |
  |     2         |      timestamp    |        10      |      3        |
  |     2         |      timestamp    |        10      |      4        |
  |     3         |      timestamp    |        5       |      1        |
  |     3         |      timestamp    |        10      |      2        |
  |     3         |      timestamp    |        10      |      3        |
  |     3         |      timestamp    |        10      |      4        |
  +---------------+-------------------+----------------+---------------+
  </code></pre>
  
  <pre><code>products
  +---------------+-------------------+
  |    id         |       names       |
  +---------------+-------------------+
  |     1         |     ice cream     |
  |     2         |     iced tea      |
  |     3         |       cake        |
  |     4         |   orange juice    |
  +---------------+-------------------+
  </code></pre>
  
  <p>this is the query I'm using</p>
  
  <pre><code>select p.names, coalesce(sum(o.qty), 0) sum_product_qty
  from products p
  left join orders_item o on p.id = o.product_id
  WHERE date(datesales) &lt;= curdate() and date(datesales) &gt;= curdate() - interval 6 day
  group by p.id, p.names
  </code></pre>
  
  <p>what I want to happen is that the query shows the items that has 0 match on the other table as such</p>
  
  <pre><code>orange juice = 18
  cake         = 24
  iced tea     = 0
  ice cream    = 0
  </code></pre>
  
  <p>with the current query, it only shows results like this</p>
  
  <pre><code>orange juice = 18
  cake         = 24
  </code></pre>