mysql查询需要很多时间

-4

在rails中的这个查询不会结束。为什么？查询是：mysql查询需要很多时间

SELECT CONCAT(f.name, ' ', f.parent_names) AS FullName, 
     stts.name AS 'Status', 
     u.name AS Unit, 
     city.name AS City, 
     hus.mobile1 AS HusbandPhone, 
     wife.mobile1 AS WifePhone, 
     f.phone AS HomePhone, 
     f.contact_initiation_date AS InitDate, 
     fh.created_at AS StatusChangeDate, 
     cmt.created_at AS CommentDate, 
     cmt.comment AS LastComment, 
     f.reconnection_date AS ReconnectionDate, 
    (SELECT GROUP_CONCAT(t.name, ' ') 
    FROM taggings tgs 
    JOIN tags t ON tgs.tag_id = t.id 
    WHERE tgs.taggable_type = 'family' 
    AND tgs.taggable_id = f.id) AS HandlingStatus 
FROM families f 
JOIN categories stts ON f.family_status_cat_id = stts.id 
JOIN units u ON f.unit_id = u.id 
JOIN categories city ON f.main_city_cat_id = city.id 
LEFT JOIN contacts hus ON f.husband_id = hus.id 
LEFT JOIN contacts wife ON f.wife_id = wife.id 
LEFT JOIN comments cmt ON f.id = cmt.commentable_id 
AND cmt.created_at = 
    (SELECT MAX(created_at) 
    FROM comments 
    WHERE commentable_id = f.id) 
LEFT JOIN family_histories fh ON f.id = fh.family_id 
AND fh.created_at = 
    (SELECT MAX(created_at) 
    FROM family_histories 
    WHERE family_id = f.id 
    AND family_history_cat_id = 1422) 
AND fh.family_history_cat_id = 1422 
WHERE 1=0 
    OR (f.family_status_cat_id = 1422 
     AND ( (SELECT MAX(_fh.created_at) 
       FROM family_histories _fh 
       WHERE _fh.family_history_cat_id = 1422 
       AND _fh.family_id = f.id 
       AND _fh.new_val LIKE '%1422%') BETWEEN '2010-03-10' AND '2011-03-02'))

我是否错过了什么？ Synatx是正确的，那么问题是什么？

来源

2013-03-06 Noam B.

你的'EXPLAIN'说什么？ – 2013-03-06 17:21:55

表索引？每个表有多少条记录？我们不能仅仅基于粘贴的查询（甚至没有格式化）来回答为什么表现不如您期望的那么好。 – 2013-03-06 17:23:44

您的个人查询是否成功运行？我会把这个调整到最低限度，然后从那里开始工作 – 2013-03-06 17:24:06

我认为问题是你必须进行很多子查询。它需要花费很多时间。

我的建议是将你通过子查询得到的一些信息存储在主表中。

另外，您可以随时尝试创建存储过程以加快过程。

致以问候

来源

2013-03-06 17:34:39 belyid

mysql查询需要很多时间

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