[英]Slow MySQL query using LEFT JOIN
我使用一个简单的左联接查询从两个单独的表中获取两行数据。 它们都拥有一个名为domain
的公共列,我将它们加入该列中,以基于一个表的访问量和其他表的收入来计算值。
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
但通过按domain
分组,它将返回需要比较的186行数据。
任何有关低效率代码或解决此问题的更好方法的建议将不胜感激!
感谢raheel打开门,这终于奏效了,执行时间为0.051sec。 :)
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
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;
从联接的右侧检查项目的值时,不需要LEFT JOIN。 INNER JOIN在这里也可以正常工作,并且可能会更快
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