【发布时间】：2010-06-11 18:39:51
【问题描述】：
关于系统： - 有创建课程和包的导师 - 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，请查看标签在此系统中的工作原理部分？下面。
以下是相关查询
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
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
问题
上述查询返回的结果是正确的（AND 逻辑按预期工作），但是对于较重的数据，查询所花费的时间惊人地增加，而对于我拥有的当前数据，与正常查询时间相比，它大约是 25 秒大约 0.005 - 0.0002 秒，这使得它完全无法使用。
由于所有可能的字段尚未编入索引，可能会导致一些延迟。标签表的标签字段被索引。 查询有问题吗？ 执行时间超过 20 秒的原因是什么？
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。
- 为存储在tutors_tag_relations 中的导师和存储在learning_packs_tag_relations 中的包标记关系。所有单独的标签都存储在标签表中。
解释查询输出：- 请看这个截图 - http://www.test.examvillage.com/Explain_query.jpg
【问题讨论】：
-
代码高亮是一个很棒的功能
-
@sandeepan-nath：我将您的查询格式化为代码（选择并按 Ctrl+K），但除非您重新格式化，否则只有少数人会查看它...
-
@Peter 谢谢。我不知道如何缩进它。如果你能说出来，我检查了stackoverflow.com/editing-help，但无法理解那部分。
-
使用这个：dpriver.com/pp/sqlformat.htm 并选择 SQL(Text) 作为输出粘贴到这里
-
@sandeepan-nath：重要的部分是代码前有 4 个空格。您可以通过选择代码并使用
Code Sample按钮 (101 010) 或按 Ctrl+K 来完成此操作。确保粘贴前正确格式化查询，然后选择它并将其格式化为代码示例。
标签： sql mysql optimization multiple-tables