Hi Nicolas,
Thank you for the quick reply. I have done as you described and now the main page under Components > HikaShop gives the follwing error message:
1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ' CONCAT('',c.category_name) as `type` FROM #__hikashop_order AS a LEFT JOIN ' at line 1 SELECT DATE_FORMAT(FROM_UNIXTIME(CAST(a.order_created AS SIGNED )+3600),'%Y %j') AS calculated_date, SUM(prod.order_product_quantity) AS total, , CONCAT('',c.category_name) as `type` FROM ko2018_hikashop_order AS a LEFT JOIN ko2018_hikashop_currency AS d ON d.currency_id = a.order_currency_id LEFT JOIN ko2018_hikashop_order_product AS prod ON prod.order_id = a.order_id LEFT JOIN ko2018_hikashop_product_category AS cat ON cat.product_id = prod.product_id LEFT JOIN ko2018_hikashop_category AS c ON c.category_id = cat.category_id WHERE a.order_type='sale' AND cat.category_id IN ('','139','22','109','26') AND a.order_created > 1342367760 AND a.order_created < 1343663760 GROUP BY c.category_id,calculated_date ORDER BY calculated_date DESC