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我正在尝试生成包含来自 EVENTSTOCKLINK 的字段的 ACTION 记录列表（如果它们存在）我的查询曾经看起来像

SELECT 
  action.actionid,
  partex.stockmake AS partexmake, 
  partex.stockmod AS partexmod
FROM
  ACTION 
  INNER JOIN EVENT 
    ON action.eventid = event.eventid 
  LEFT JOIN 
    (SELECT registrationnumber,stockmake,stockmod,stocktran,eventid 
    FROM eventstocklink 
  LEFT JOIN stock ON stock.stockid = eventstocklink.stockid 
WHERE statusid = '5'
GROUP BY eventstocklink.eventid
) AS partex 
ON partex.eventid = event.eventid 
WHERE actiondate2 BETWEEN 20130601 
  AND 20131031 
  AND event.siteid = 1 
  AND action.typeid = 1

这个查询需要 >4 秒 - 所以按照线程的建议，我一直在 SELECT 行中运行子查询，并且可以通过创建这样的查询来减少运行时间

SELECT action.actionid,
 (SELECT stockmake FROM eventstocklink
  LEFT JOIN stock ON stock.stockid = eventstocklink.stockid 
  WHERE statusid = '5' AND eventstocklink.eventid = event.eventid
 GROUP BY eventstocklink.eventid) partexmake,
 (SELECT stockmod FROM eventstocklink
  LEFT JOIN stock ON stock.stockid = eventstocklink.stockid 
  WHERE statusid = '5' AND eventstocklink.eventid = event.eventid
 GROUP BY eventstocklink.eventid) partexmod
FROM
  ACTION 
  INNER JOIN EVENT 
    ON action.eventid = event.eventid 
WHERE actiondate2 BETWEEN 20130601 
  AND 20131031 
  AND event.siteid = 1 
  AND action.typeid = 1

这是构建此查询的最佳方式吗 - 我想包含更多来自 STOCK 表的“statusid=5”字段

4

1 回答 1

1

您的新查询具有相关的子查询，这些子查询往往表现不佳，而我不确定子查询在您的原始查询中是否必要。

了解表的索引会有所帮助，因为我怀疑这些是您当前查询困难的真正原因（例如，eventstocklink.eventid 上是否有索引）。

尝试这样的事情： -

SELECT 
  action.actionid,
  MAX(partex.stockmake) AS partexmake, 
  MAX(partex.stockmod) AS partexmod
FROM ACTION 
INNER JOIN EVENT 
ON action.eventid = event.eventid 
LEFT JOIN eventstocklink
ON eventstocklink.eventid = event.eventid
LEFT JOIN stock 
ON stock.stockid = eventstocklink.stockid 
AND stock.statusid = '5'
WHERE actiondate2 BETWEEN 20130601 AND 20131031 
AND event.siteid = 1 
AND action.typeid = 1 
GROUP BY action.actionid

这确实假设如果有多个匹配的查询，您并不真正关心返回哪个 stockmake 或 stockmod（因为您现有的查询不会尝试定义返回哪些查询）。

于 2013-10-17T12:02:32.547 回答