Question

我有MySQL查询，大约需要25秒。行数不多（大约200行），但我不明白为什么需要很长时间。

查询：

SELECT *
     , c.id c_id
  FROM campaign c 
  JOIN campaign_category cc 
    ON c.campaign_type = cc.id
 WHERE c.is_deleted = 0
   AND c.status = 1
   AND c.id NOT IN (SELECT campaign_id FROM user_reviews WHERE user_id = 4)
   AND c.amt_req > (SELECT COUNT(id) 
                      FROM reserved_reviews 
                     WHERE camping_id = c.id 
                       AND user_id != 4) 
                 + (SELECT COUNT(id) 
                      FROM user_reviews 
                     WHERE campaign_id = c.id)

编辑：我尝试了这样的JOIN，但没有结果：

SELECT 
  *, `c`.`id` as `c_id`,COUNT(`ur`.`id`) as `total_reviewed`, COUNT(`rr`.`id`) as `total_reserved`
FROM 
`campaign` `c`
JOIN `campaign_category` `cc` ON `c`.`campaign_type`=`cc`.`id`
JOIN `user_reviews` `ur` ON `ur`.`campaign_id`=`c`.`id`
JOIN `reserved_reviews` `rr` ON `rr`.`camping_id`=`c`.`id`
WHERE 
     `c`.`is_deleted` =0
AND 
      `c`.`status` = 1
AND 
       `ur`.`user_id` != 4 
GROUP BY `c`.`id`
HAVING `c`.`amt_req` > COUNT(`ur`.`id`) + COUNT(`rr`.`id`)

编辑：表结构：第一个图像 - user_reviews表，第二个图像campagin表，第三个图像：reserved_reviews表。

http://imgur.com/GI4817B,SdnSxuz,truxHM6#0

Answer 1

您可以使用索引改进此查询;

SELECT *, c.id c_id
FROM campaign c JOIN
     campaign_category cc 
     ON c.campaign_type = cc.id
WHERE c.is_deleted = 0 AND
      c.status = 1 AND
      c.id NOT IN (SELECT campaign_id FROM user_reviews WHERE user_id = 4)
      c.amt_req > (SELECT COUNT(*) 
                   FROM reserved_reviews 
                   WHERE campaign_id = c.id AND user_id <> 4)
                  ) +
                  (SELECT COUNT(id) 
                   FROM user_reviews 
                   WHERE campaign_id = c.id
                  ) ;

对于外部查询和连接：campaign(status, is_deleted, id, amt_req)和campaign_category(id)（如果将后者定义为主键，则应该使用后者。

然后：user_reviews(user_id, campaign_id)，reserved_reviews(campaign_id, user_id)和user_reviews(campaign_id)。

MySQL查询太慢约25秒

1 个答案: