Question

我正在使用一个简单的左连接查询从两个单独的表中获取两行数据。它们都包含一个名为domain的公共列，我将其加入此列，以根据一个表访问和其他表收入计算值。

SELECT t1.`domain` AS `domain`,
       (SUM(earnings)/SUM(visits)) AS `rpv` 
FROM   hat_adsense_stats t1 
LEFT JOIN hat_analytics_stats t4 ON t4.`domain`=t1.`domain`  
WHERE(t1.`hat_analytics_id`='91' OR t1.`hat_analytics_id`='92') 
       AND t1.`date`>='2013-02-18' 
       AND t4.`date`>='2013-02-18' 
GROUP BY t1.`domain` 
ORDER BY rpv DESC 
LIMIT 10;

这是我运行的查询，执行时需要9.060秒。

hat_adsense_stats表包含60887条记录 hat_analytics_stats表包含190780条记录

但是按domain分组，它会返回需要比较的186行数据。

任何有关无效代码或更好解决方法的建议都将受到赞赏！

Answer 1

谢谢raheel打开门，这最终有效，执行时间为0.051秒。：）

SELECT 
    t1.`domain` AS `domain`, 
    SUM(earnings)/visits AS `rpv` 
FROM hat_adsense_stats t1 
    INNER JOIN (SELECT 
        domain, 
        SUM(visits) AS visits 
        FROM hat_analytics_stats 
        WHERE `date` >= "2013-02-18" 
        GROUP BY domain) AS t4 
    ON t4.domain = t1.domain  
WHERE t1.`hat_analytics_id` IN('91','92') 
AND t1.`date`>='2013-02-18' 
GROUP BY t1.`domain` 
ORDER BY rpv DESC 
LIMIT 10

Answer 2

像这样更改您的查询

SELECT
  t1.`domain`           AS `domain`,
  t2.earnings/t2.visits AS `rpv`
FROM hat_adsense_stats t1
  INNER JOIN (SELECT
                domain,
                sum(earnings)          AS earnings,
                SUM(visits)            AS visits
             FROM hat_adsense_stats
             GROUP BY domain) AS t2
    on t2.domain = t1.domain
  LEFT JOIN hat_analytics_stats t4
    ON t4.`domain` = t1.`domain`
WHERE t1.`hat_analytics_id` IN('91','92')
    AND t1.`date` >= '2013-02-18'
    AND t4.`date` >= '2013-02-18'
GROUP BY t1.`domain`
ORDER BY rpv DESC
LIMIT 10;

Answer 3

当您从联接的右侧检查项目的值时，不需要LEFT JOIN。内部联接在这里也可以正常工作，可能会更快

使用LEFT JOIN减慢MySQL查询

3 个答案: