我有一个包含下表的数据库
german_akkusativ_plural [ akkusativ_plural, word_id ]
german_akkusativ_singular [ akkusativ_singular, word_id ]
german_dativ_plural [ dativ_plural, word_id ]
german_dativ_singular [ dativ_singular, word_id ]
german_gender [ gender, word_id ]
german_genitiv_plural [ genitiv_plural, word_id ]
german_genitiv_singular [ genitiv_singular, word_id ]
german_nominativ_plural [ nominativ_plural, word_id ]
german_nominativ_singular [ nominativ_singular, word_id ]
german_word [ id, word, blacklisted ]
下面的查询应该找到一个单词对应的性别(该单词可以是其中一种情况)
SELECT gg.gender
FROM german_word gw
INNER JOIN
german_nominativ_singular gns
ON gw.id = gns.word_id
INNER JOIN
german_nominativ_plural gnp
ON gw.id = gnp.word_id
INNER JOIN
german_akkusativ_singular gas
ON gw.id = gas.word_id
INNER JOIN
german_akkusativ_plural gap
ON gw.id = gap.word_id
INNER JOIN
german_dativ_singular gds
ON gw.id = gds.word_id
INNER JOIN
german_dativ_plural gdp
ON gw.id = gdp.word_id
INNER JOIN
german_genitiv_singular ggs
ON gw.id = ggs.word_id
INNER JOIN
german_genitiv_plural ggp
ON gw.id = ggp.word_id
INNER JOIN
german_gender gg
ON gw.id = gg.word_id
WHERE
gns.nominativ_singular = 'Auto' OR
gnp.nominativ_plural = 'Auto' OR
gas.akkusativ_singular = 'Auto' OR
gap.akkusativ_plural = 'Auto' OR
gds.dativ_singular = 'Auto' OR
gdp.dativ_plural = 'Auto' OR
ggs.genitiv_singular = 'Auto' OR
ggp.genitiv_plural = 'Auto'
问题是，当我在 phpMyAdmin 中运行查询时，需要大约 150 秒才能运行。这是为什么？我对除“黑名单”之外的所有字段都有索引。
这是正确的方法还是我完全偏离了轨道？
我将非常感谢任何帮助!谢谢。
编辑:
这是 EXPLAIN 的输出
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE gg ALL word_id NULL NULL NULL 41522
1 SIMPLE gdp ref dativ_plural,word_id word_id 5 usr_web410_3.gg.word_id 1 Using where
1 SIMPLE ggp ref genitiv_plural,word_id word_id 5 usr_web410_3.gg.word_id 1 Using where
1 SIMPLE gap ref akkusativ_plural,word_id word_id 5 usr_web410_3.gg.word_id 1 Using where
1 SIMPLE gnp ref nominativ_plural,word_id word_id 5 usr_web410_3.ggp.word_id 1 Using where
1 SIMPLE gas ref akkusativ_singular,word_id word_id 5 usr_web410_3.gg.word_id 1 Using where
1 SIMPLE gns ref nominativ_singular,word_id word_id 5 usr_web410_3.gg.word_id 1 Using where
1 SIMPLE gds ref dativ_singular,word_id word_id 5 usr_web410_3.gns.word_id 1 Using where
1 SIMPLE ggs ref genitiv_singular,word_id word_id 5 usr_web410_3.gg.word_id 1 Using where
1 SIMPLE gw eq_ref PRIMARY PRIMARY 4 usr_web410_3.gg.word_id 1 Using index
最佳答案
您正在获取每个表中的每一行，然后检查是否有任何表与'Auto'匹配。这很慢。这些OR对性能不利，因此您必须放弃它们。
有很多方法可以重写您的查询，我只推荐一种。
首先，我认为没有理由使用 german_word 表。它不存在于任何 where 或 select 子句中，因此我们可以只使用 german_gender 表。请记住，更大的 SQL 查询并不一定意味着性能更差。
试试这个。它应该更快地带来相同的结果。我假设所有文本列(例如 nominativ_singular)都已建立索引。
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_nominativ_singular gns
ON gg.word_id = gns.word_id AND gns.nominativ_singular = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_nominativ_plural gnp
ON gg.word_id = gnp.word_id AND gnp.nominativ_plural = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_akkusativ_singular gas
ON gg.word_id = gas.word_id AND gas.akkusativ_singular = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_akkusativ_plural gap
ON gg.word_id = gap.word_id AND gap.akkusativ_plural = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_dativ_singular gds
ON gg.word_id = gds.word_id AND gds.dativ_singular = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_dativ_plural gdp
ON gg.word_id = gdp.word_id AND gdp.dativ_plural = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_genitiv_singular ggs
ON gg.word_id = ggs.word_id AND ggs.genitiv_singular = 'Auto'
UNION
SELECT gg.gender as gender
FROM german_gender gg
INNER JOIN german_genitiv_plural ggp
ON gg.word_id = ggp.word_id AND ggp.genitiv_plural = 'Auto'
关于mysql - MySQL 查询 153 秒，我做错了什么？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20373240/