Mysql Query占用了太多时间

Question

我需要从产品表中获取所有记录，并且只匹配其他表中的记录。 我在产品表中有多达2000条记录的mysql表。没有group_concate和group by的连接查询运行得更快。 e.x以下查询需要0.6486秒

SELECT *    FROM  `oc_product` 
LEFT JOIN  `oc_product_to_category` ON  `oc_product`.`product_id` =  `oc_product_to_category`.`product_id` 
LEFT JOIN  `oc_product_description` ON  `oc_product`.`product_id` =  `oc_product_description`.`product_id` 
LEFT JOIN  `oc_category_description` ON  `oc_product_to_category`.`category_id` =  `oc_category_description`.`category_id` 
LEFT JOIN  `oc_product_image` ON  `oc_product_to_category`.`product_id` =  `oc_product_image`.`product_id` 
LEFT JOIN  `oc_seo_data` ON  `oc_product`.`product_id` =  `oc_seo_data`.`id` 
LEFT JOIN  `oc_url_alias` ON  `oc_seo_data`.`url_alias_id` =  `oc_url_alias`.`url_alias_id` 

当我使用GROUP BY和CONCAT_GROUP时，需要18.4205秒

    SELECT `oc_product_description`.`name` as `Product_Name`,`oc_product`.`price` as `PRICE`,`oc_url_alias`.`keyword` as `Product_Url`,`oc_product_image`.`image` as `Image Path`,GROUP_CONCAT(distinct `oc_category_description`.`name`) as `Category_name`,`oc_product`.`model` as `Product_Code` FROM `oc_product` LEFT JOIN  `oc_product_to_category` ON `oc_product`.`product_id` = `oc_product_to_category`.`product_id`
    LEFT JOIN `oc_product_description` ON `oc_product`.`product_id` = `oc_product_description`.`product_id`
    LEFT JOIN `oc_category_description` ON `oc_product_to_category`.`category_id` = `oc_category_description`.`category_id`
    LEFT JOIN `oc_product_image` ON `oc_product_to_category`.`product_id` = `oc_product_image`.`product_id`
    LEFT  JOIN `oc_seo_data` ON `oc_product`.`product_id` = `oc_seo_data`.`id`
    left JOIN `oc_url_alias` on `oc_seo_data`.`url_alias_id` = `oc_url_alias` .`url_alias_id`
    GROUP BY `oc_product`.`product_id`