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关于系统：

- 系统共有 8 个表 - Users - Tutor_Details（Tutors 是 User 的一种，Tutor_Details 表链接到 Users） - learning_packs，（存储由导师创建的包） - learning_packs_tag_relations，（保存用于搜索的标签关系） - utors_tag_relations 和标签和订单（包含导师包的购买细节），order_details 链接到订单和tutor_details。

要更清楚地了解所涉及的表格，请查看最后的表格部分。

- 正在遵循基于标签的搜索方法。当新导师注册和导师创建包时创建标签关系（这使得导师和包可搜索）。有关详细信息，请查看标签如何在此系统中工作？以下。

以下是我试图优化的更复杂查询的更简单表示（不是实际的）：-我使用explanation of parts了查询中的语句

==================================================== ===========================

select 

SUM(DISTINCT( t.tag LIKE "%Dictatorship%" )) as key_1_total_matches, 
SUM(DISTINCT( t.tag LIKE "%democracy%" )) as key_2_total_matches,
td.*, u.*, count(distinct(od.id_od)), `if (lp.id_lp > 0) then some conditional logic on lp fields else 0 as tutor_popularity`

from Tutor_Details AS td JOIN Users as u on u.id_user = td.id_user 

LEFT JOIN Learning_Packs_Tag_Relations AS lptagrels ON td.id_tutor = lptagrels.id_tutor 
LEFT JOIN Learning_Packs AS lp ON lptagrels.id_lp = lp.id_lp 
LEFT JOIN `some other tables on lp.id_lp - let's call learning pack tables set (including 

Learning_Packs table)`

LEFT JOIN Order_Details as od on td.id_tutor = od.id_author LEFT JOIN Orders as o on 

od.id_order = o.id_order 

LEFT JOIN Tutors_Tag_Relations as ttagrels ON td.id_tutor = ttagrels.id_tutor 

JOIN Tags as t on (t.id_tag = ttagrels.id_tag) OR (t.id_tag = lptagrels.id_tag) 

where `some condition on Users table's fields`

AND CASE WHEN ((t.id_tag = lptagrels.id_tag) AND (lp.id_lp > 0)) THEN `some 

conditions on learning pack tables set` ELSE 1 END

 AND CASE WHEN ((t.id_tag = wtagrels.id_tag) AND (wc.id_wc > 0)) THEN `some 

conditions on webclasses tables set` ELSE 1 END

 AND CASE WHEN (od.id_od>0) THEN od.id_author = td.id_tutor and `some conditions on Orders table's fields` ELSE 1 END

 AND ( t.tag LIKE "%Dictatorship%" OR t.tag LIKE "%democracy%")

group by td.id_tutor HAVING key_1_total_matches = 1 AND key_2_total_matches = 1
order by tutor_popularity desc, u.surname asc, u.name asc limit 
0,20

==================================================== ====================

上面的查询是做什么的？

  • 是否对搜索关键字进行 AND 逻辑搜索（本例中为 2 - “民主”和“独裁”）。
  • 仅返回两个关键字都存在于两个集合中的那些导师 - 导师详细信息和导师创建的所有包的详细信息。

为了清楚起见 - 假设一个名为“Sandeepan Nath”的导师创建了一个包“我的第一个包”，那么：-

  • 搜索“Sandeepan Nath”会返回 Sandeepan Nath。
  • 搜索“Sandeepan first”会返回 Sandeepan Nath。
  • 搜索“Sandeepan second”不会返回 Sandeepan Nath。

==================================================== =====================================

问题

上述查询返回的结果是正确的（AND 逻辑按预期工作），但是在重负载数据库上查询所花费的时间大约为 25 秒，而正常查询时间为 0.005 - 0.0002 秒，这使得它完全无法使用。

由于尚未对所有可能的字段进行索引，可能会导致一些延迟，但我希望有一个更好的查询作为解决方案，尽可能优化，显示相同的结果

==================================================== =========================================

标签在这个系统中是如何工作的？

  • 当导师注册时，会输入标签并根据导师的详细信息（如姓名、姓氏等）创建标签关系。
  • 当导师创建包时，再次输入标签并根据包的详细信息（如包名称、描述等）创建标签关系。
  • 存储在tutors_tag_relations 中的导师的标签关系和存储在learning_packs_tag_relations 中的包的标签关系。所有单个标签都存储在标签表中。

==================================================== ===================

桌子

以下大部分表格包含许多其他字段，我在这里省略了。

CREATE TABLE IF NOT EXISTS `users` (
  `id_user` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(100) NOT NULL DEFAULT '',
  `surname` varchar(155) NOT NULL DEFAULT '',
  PRIMARY KEY (`id_user`)
  ) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=636 ;

CREATE TABLE IF NOT EXISTS `tutor_details` (
  `id_tutor` int(10) NOT NULL AUTO_INCREMENT,
  `id_user` int(10) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id_tutor`),
  KEY `Users_FKIndex1` (`id_user`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=51 ;



CREATE TABLE IF NOT EXISTS `orders` (
  `id_order` int(10) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id_order`),
  KEY `Orders_FKIndex1` (`id_user`),
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=275 ;

ALTER TABLE `orders`
  ADD CONSTRAINT `Orders_ibfk_1` FOREIGN KEY (`id_user`) REFERENCES `users` 

(`id_user`) ON DELETE NO ACTION ON UPDATE NO ACTION;



CREATE TABLE IF NOT EXISTS `order_details` (
  `id_od` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_order` int(10) unsigned NOT NULL DEFAULT '0',
  `id_author` int(10) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id_od`),
  KEY `Order_Details_FKIndex1` (`id_order`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=284 ;

ALTER TABLE `order_details`
  ADD CONSTRAINT `Order_Details_ibfk_1` FOREIGN KEY (`id_order`) REFERENCES `orders` 

(`id_order`) ON DELETE NO ACTION ON UPDATE NO ACTION;



CREATE TABLE IF NOT EXISTS `learning_packs` (
  `id_lp` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `id_author` int(10) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`id_lp`),
  KEY `Learning_Packs_FKIndex2` (`id_author`),
  KEY `id_lp` (`id_lp`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=23 ;


CREATE TABLE IF NOT EXISTS `tags` (
  `id_tag` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `tag` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id_tag`),
  UNIQUE KEY `tag` (`tag`),
  KEY `id_tag` (`id_tag`),
  KEY `tag_2` (`tag`),
  KEY `tag_3` (`tag`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3419 ;



CREATE TABLE IF NOT EXISTS `tutors_tag_relations` (
  `id_tag` int(10) unsigned NOT NULL DEFAULT '0',
  `id_tutor` int(10) DEFAULT NULL,
  KEY `Tutors_Tag_Relations` (`id_tag`),
  KEY `id_tutor` (`id_tutor`),
  KEY `id_tag` (`id_tag`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE `tutors_tag_relations`
  ADD CONSTRAINT `Tutors_Tag_Relations_ibfk_1` FOREIGN KEY (`id_tag`) REFERENCES 

`tags` (`id_tag`) ON DELETE NO ACTION ON UPDATE NO ACTION;


CREATE TABLE IF NOT EXISTS `learning_packs_tag_relations` (
  `id_tag` int(10) unsigned NOT NULL DEFAULT '0',
  `id_tutor` int(10) DEFAULT NULL,
  `id_lp` int(10) unsigned DEFAULT NULL,
  KEY `Learning_Packs_Tag_Relations_FKIndex1` (`id_tag`),
  KEY `id_lp` (`id_lp`),
  KEY `id_tag` (`id_tag`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE `learning_packs_tag_relations`
  ADD CONSTRAINT `Learning_Packs_Tag_Relations_ibfk_1` FOREIGN KEY (`id_tag`) 

REFERENCES `tags` (`id_tag`) ON DELETE NO ACTION ON UPDATE NO ACTION;

==================================================== ==================================

以下是确切的查询（这也包括课程 - 导师可以创建课程并且搜索词与导师创建的课程相匹配）：-

SELECT SUM(DISTINCT( t.tag LIKE "%Dictatorship%" )) AS key_1_total_matches,
       SUM(DISTINCT( t.tag LIKE "%democracy%" ))    AS key_2_total_matches,
       COUNT(DISTINCT( od.id_od ))                  AS tutor_popularity,
       CASE
         WHEN ( IF(( wc.id_wc > 0 ), ( wc.wc_api_status = 1
                                       AND wc.wc_type = 0
                                       AND wc.class_date > '2010-06-01 22:00:56'
                                       AND wccp.status = 1
                                       AND ( wccp.country_code = 'IE'
                                              OR wccp.country_code IN ( 'INT' )
                                           ) ), 0)
              ) THEN 1
         ELSE 0
       END                                          AS 'classes_published',
       CASE
         WHEN ( IF(( lp.id_lp > 0 ), ( lp.id_status = 1
                                       AND lp.published = 1
                                       AND lpcp.status = 1
                                       AND ( lpcp.country_code = 'IE'
                                              OR lpcp.country_code IN ( 'INT' )
                                           ) ), 0)
              ) THEN 1
         ELSE 0
       END                                          AS 'packs_published',
       td . *,
       u . *
FROM   tutor_details AS td
       JOIN users AS u
         ON u.id_user = td.id_user
       LEFT JOIN learning_packs_tag_relations AS lptagrels
         ON td.id_tutor = lptagrels.id_tutor
       LEFT JOIN learning_packs AS lp
         ON lptagrels.id_lp = lp.id_lp
       LEFT JOIN learning_packs_categories AS lpc
         ON lpc.id_lp_cat = lp.id_lp_cat
       LEFT JOIN learning_packs_categories AS lpcp
         ON lpcp.id_lp_cat = lpc.id_parent
       LEFT JOIN learning_pack_content AS lpct
         ON ( lp.id_lp = lpct.id_lp )
       LEFT JOIN webclasses_tag_relations AS wtagrels
         ON td.id_tutor = wtagrels.id_tutor
       LEFT JOIN webclasses AS wc
         ON wtagrels.id_wc = wc.id_wc
       LEFT JOIN learning_packs_categories AS wcc
         ON wcc.id_lp_cat = wc.id_wp_cat
       LEFT JOIN learning_packs_categories AS wccp
         ON wccp.id_lp_cat = wcc.id_parent
       LEFT JOIN order_details AS od
         ON td.id_tutor = od.id_author
       LEFT JOIN orders AS o
         ON od.id_order = o.id_order
       LEFT JOIN tutors_tag_relations AS ttagrels
         ON td.id_tutor = ttagrels.id_tutor
       JOIN tags AS t
         ON ( t.id_tag = ttagrels.id_tag )
             OR ( t.id_tag = lptagrels.id_tag )
             OR ( t.id_tag = wtagrels.id_tag )
WHERE  ( u.country = 'IE'
          OR u.country IN ( 'INT' ) )
       AND CASE
             WHEN ( ( t.id_tag = lptagrels.id_tag )
                    AND ( lp.id_lp > 0 ) ) THEN lp.id_status = 1
                                                AND lp.published = 1
                                                AND lpcp.status = 1
                                                AND ( lpcp.country_code = 'IE'
                                                       OR lpcp.country_code IN (
                                                          'INT'
                                                          ) )
             ELSE 1
           END
       AND CASE
             WHEN ( ( t.id_tag = wtagrels.id_tag )
                    AND ( wc.id_wc > 0 ) ) THEN wc.wc_api_status = 1
                                                AND wc.wc_type = 0
                                                AND
             wc.class_date > '2010-06-01 22:00:56'
                                                AND wccp.status = 1
                                                AND ( wccp.country_code = 'IE'
                                                       OR wccp.country_code IN (
                                                          'INT'
                                                          ) )
             ELSE 1
           END
       AND CASE
             WHEN ( od.id_od > 0 ) THEN od.id_author = td.id_tutor
                                        AND o.order_status = 'paid'
                                        AND CASE
             WHEN ( od.id_wc > 0 ) THEN od.can_attend_class = 1
             ELSE 1
                                            END
             ELSE 1
           END
GROUP  BY td.id_tutor
HAVING key_1_total_matches = 1
       AND key_2_total_matches = 1
ORDER  BY tutor_popularity DESC,
          u.surname ASC,
          u.name ASC
LIMIT  0, 20

请注意 - 提供的数据库结构未显示此查询中的所有字段和表

==================================================== ====================================

解释查询输出：- 请看这个截图 http://www.test.examvillage.com/Explain_query.jpg

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4 回答 4

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你的问题是，“我怎样才能找到符合某些标签的导师？” 这不是一个很难的问题，所以回答它的查询也不应该很难。

就像是：

SELECT *
FROM tutors
WHERE tags LIKE '%Dictator%' AND tags LIKE '%Democracy%'

如果您修改您的设计以在“导师”表中有一个“标签”字段，那么这将起作用，您可以在其中放置适用于该导师的所有标签。它将消除连接和表层。

是所有这些层的连接和表都提供了真正的功能，还是只是更多的编程难题？想想你的应用真正需要的功能，然后简化你的数据库设计！！

于 2010-06-08T21:33:26.167 回答
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回答我自己的问题。

这种方法的主要问题是在单个查询中连接了太多表。当与如此多的表连接时，其中一些表Tags（具有大量记录 -​​ 将来可以保存与词汇表中所有英语单词一样多的记录）会导致这种乘法效应，这是无法抵抗的。

解决方案基本上是确保在单个查询中没有进行过多的连接。将一个大型连接查询分解为多个步骤，将一个查询的结果（涉及某些表上的连接）用于下一个连接查询（涉及其他表上的连接）会降低乘法效应。

稍后我将尝试对此提供更好的解释。

于 2011-04-20T13:33:36.343 回答
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有关行数、值分布、索引、数据库大小、内存大小、磁盘布局的信息 - RAID 0、5 等 - 当查询速度较慢时有多少用户正在访问您的数据库 - 正在运行的其他查询。所有这些因素都会影响性能。

如果它只是一个查询/索引问题，那么解释计划输出的打印输出可能会阐明原因。也需要确切的查询。

于 2010-06-08T20:53:11.880 回答
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  1. 您确实应该为查询使用一些更好的格式。只需在每行的开头添加至少 4 个空格即可获得这种漂亮的代码格式。

    SELECT * FROM sometable
    INNER JOIN anothertable ON sometable.id = anothertable.sometable_id

    或者看看这里：https ://stackoverflow.com/editing-help

  2. 你能提供mysql的执行计划吗？您需要在查询中添加“EXPLAIN”并复制结果。

    EXPLAIN SELECT * FROM ...complexquery...

    会给你一些有用的提示（执行顺序、返回的行、可用/使用的索引）

于 2010-06-08T21:16:01.517 回答