我有一个查询:优化SQL查询运行
SELECT `l`.`id`, `l`.`headline`, `l`.`description`, `l`.`image`, `l`.`campaign_id`, IF(l.required_impressions=0,0,1) AS sequence, (IFNULL(ROUND(COUNT(DISTINCT(lc.id))/COUNT(DISTINCT(li.id)), 3) * 100, 0) * 0.3) + (l.cost * 0.7) AS `scales`, `c`.`name` AS `campaign`
FROM `app_links` AS `l`
INNER JOIN `app_campaigns` AS `c` ON c.id = l.campaign_id
LEFT JOIN `app_link_clicks` AS `lc` ON lc.link_id = l.id
LEFT JOIN `app_link_impressions` AS `li` ON li.link_id = l.id
LEFT JOIN `app_links_categories` AS `lcat` ON l.id = lcat.link_id
LEFT JOIN `app_links_countries` AS `lcou` ON l.id = lcou.link_id
WHERE lcat.category_id IN(3,7,14)
AND lcou.country_id IN(89,147,124,131,259,197,88)
GROUP BY `l`.`id`
ORDER BY sequence DESC, `scales` DESC
LIMIT 6
的EXPLAIN查询返回:
你有什么想法如何优化查询?现在,它采取〜0.6秒,所以这是相当长的:/
取下提供模式来自查询的'lcat'和'lcou'项,因为它们没有被引用? (或者用一个普通的'JOIN'替换'LEFT JOIN',的确如此) – wildplasser
是否有意使用'lcou.country_id'和'lcou'加入'LEFT JOIN'? 'lcat'的同一个问题。 – zerkms
@wildplasser:它们被用在'WHERE'里。 – zerkms