How to convert sub query to joins?
<p>I am using this query in my opencart site</p>

<pre><code>SELECT  MIN(tmp.date_added) AS date_start,
        MAX(tmp.date_added) AS date_end,
        COUNT(tmp.order_id) AS `orders`,
        SUM(tmp.products) AS products,
        SUM(tmp.tax) AS tax,
        SUM(tmp.total) AS total
    FROM  
      ( SELECT  o.order_id, 
              ( SELECT  SUM(op.quantity)
                    FROM  `oc_order_product` op
                    WHERE  op.order_id = o.order_id
                    GROUP BY  op.order_id
              ) AS products, 
              ( SELECT  SUM(ot.value)
                    FROM  `oc_order_total` ot
                    WHERE  ot.order_id = o.order_id
                      AND  ot.code = 'tax'
                    GROUP BY  ot.order_id
              ) AS tax,
              o.total,
              o.date_added
            FROM  `oc_order` o
            WHERE  o.order_status_id &gt; '0'
              AND  DATE(o.date_added) &gt;= '2015-03-01'
              AND  DATE(o.date_added) &lt;= '2016-04-19'
            GROUP BY  o.order_id
      ) tmp
    GROUP BY  WEEK(tmp.date_added)
    ORDER BY  tmp.date_added DESC
    LIMIT  0,60
</code></pre>

<p>Queries like this make my site very slow. Is there any easy way to convert  this query from sub query to joins.
Here is the output of above query
<a href="https://i.stack.imgur.com/F34RM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/F34RM.png" alt="enter image description here"></a></p>