Question

运行此查询时：

SELECT
    a.id,
    pub.name AS publisher_name,
    pc.name AS placement_name,
    b.name AS banner_name,
    a.lead_id,
    a.partner_id,
    a.type,
    l.status,
    s.correctness,
    a.landing_page,
    t.name AS tracker_name,
    a.date_view,
    a.date_action

FROM actions AS a
LEFT JOIN publishers AS pub ON a.publisher_id = pub.id
LEFT JOIN placements AS pc ON pc.publisher_id = pub.id
LEFT JOIN banners AS b ON b.campaign_id = a.campaign_id
LEFT JOIN leads l ON
    l.lead_id = a.lead_id
    AND l.created = (
        SELECT MAX(created) from leads l2 where l2.lead_id = l.lead_id
    )
LEFT JOIN statuses AS s ON l.status = s.status
LEFT JOIN trackers AS t ON t.id = a.tracker_id
LIMIT 10

我可以按actions表中的每一列进行排序。但是，当我尝试ORDER BY b.name（来自banners表，加入actions.banner_id）或ORDER BY l.lead_id（加入leads处于更复杂的情况时），如上所示）MySQL运行查询的时间很长（大多数表都有数万条记录）。在性能方面，是否可以按连接列进行排序？

Answer 1

您应该在要排序的列的表上使用内部联接重写查询。

例如，如果您对actions.banner_id

进行排序

SELECT ...
FROM actions AS a
  JOIN banners AS b ON b.campaign_id = a.campaign_id
  LEFT JOIN  *rest of the query*

除非没有足够的横幅可以加入行动以产生总共10行，否则您将获得相同的结果。

我猜不是这样，否则你不会在banner_id上排序。

Answer 2

您可以先在子查询中过滤（按顺序，在哪里等）记录，然后将结果与其余表格连接起来。

从连接中排序结果

2 个答案: