如何优化这个MySQL查询/结构？

Question

我在这里得到了这个大问题：

SELECT `l`.`web_id`, `rn`.`resort_id`, `rn`.`name`,
    `rn`.`address1`, `rn`.`city`, `rn`.`state`, `rn`.`postal_code`,
    `rn`.`country`, `p`.`picture_name`, `p`.`picture_url`,
    `ra`.`destination`, COUNT(`d`.`web_id`) AS `adsnum` 
FROM `resort_name` `rn` 
LEFT JOIN `location` `l` ON `rn`.`name`=`l`.`property_name` 
LEFT JOIN `pictures` `p` ON `p`.`resort_id`=`rn`.`resort_id`
    AND `p`.`picture_name` = (
        SELECT `picture_name` FROM `pictures`
        WHERE `resort_id`=`rn`.`resort_id`
        ORDER BY `priority` ASC
        LIMIT 1
    ) 
LEFT JOIN `addata` `d` ON `d`.`web_id`=`l`.`web_id` 
    AND `d`.`caption_header`="Sale"
    AND `d`.`price_desc` != "Sold"
    AND `d`.`frea`="1"
LEFT JOIN `resort_attributes` `ra` ON `ra`.`resort_id`=`rn`.`resort_id` 
WHERE `rn`.`name` != ""
    AND `rn`.`status`="Active"
    AND `rn`.`name` LIKE "%test%"
GROUP BY `rn`.`name` 
ORDER BY `rn`.`name` ASC 
LIMIT 0, 50

查询需要80秒以上才能运行。 解释说明结果图如下：

我相信这就是那种杀死表演的ALL。

如何正确索引表以提高性能？

感谢。

Answer 1

未经测试，但你可以尝试将依赖子查询重写为连接，尽管在这种复杂程度上很难预见MySQL的优化器能否做得更好;

SELECT `l`.`web_id`, `rn`.`resort_id`, `rn`.`name`,
    `rn`.`address1`, `rn`.`city`, `rn`.`state`, `rn`.`postal_code`,
    `rn`.`country`, `p`.`picture_name`, `p`.`picture_url`,
    `ra`.`destination`, COUNT(`d`.`web_id`) AS `adsnum` 
FROM `resort_name` `rn` 
LEFT JOIN `location` `l` 
  ON `rn`.`name`=`l`.`property_name` 
LEFT JOIN `pictures` `p` 
  ON `p`.`resort_id`=`rn`.`resort_id`
LEFT JOIN `pictures` `p2` 
  ON `p2`.`resort_id`=`rn`.`resort_id`
 AND `p`.priority > `p2`.`priority`
LEFT JOIN `addata` `d` 
  ON `d`.`web_id`=`l`.`web_id` 
 AND `d`.`caption_header`="Sale"
 AND `d`.`price_desc` != "Sold"
 AND `d`.`frea`="1"
LEFT JOIN `resort_attributes` `ra` 
  ON `ra`.`resort_id`=`rn`.`resort_id` 
WHERE `rn`.`status`='Active'
  AND `rn`.`name` LIKE '%test%'
  AND `p2`.`priority` IS NULL
GROUP BY `rn`.`name` 
ORDER BY `rn`.`name` ASC 
LIMIT 0, 50