Mysql SQL查询非常慢

我有这个模式，这将坐在一个爬虫的后面<代码>mitza.mine.nu 我不擅长SQL，并且我遇到了接近的结果。但问题是 快到尽头了。因为2个单词几乎需要一分钟，而

3个单词永远需要
在4555条记录上

。（当前生命样本运行另一个查询）

que做到了这一点：

搜索

w1 w2

中的单词点击DICT并获取单词id。这是在一个单独的系统中完成的 询问

从word id（

271和8596，例如

）选择所有记录并按排序
（所有记录都包含按权重和排序的两个单词），然后是按权重排序的单词1和单词2

SELECT DISTINCT(links.linkid),domain.ip,links.linkid,
links.url,words.weight,words.wordid 
FROM links 
JOIN words ON (words.linkid=links.linkid) 
JOIN domain ON (domain.siteid=links.siteid) 
WHERE links.linkid IN (SELECT linkid FROM words WHERE wordid=271)
AND links.linkid IN (SELECT linkid FROM words WHERE wordid=8596)
ORDER BY words.weight DESC LIMIT 0, 8

---

尝试以下查询，避免重复调用链接表

SELECT DISTINCT(links.linkid),domain.ip,links.linkid,
    links.url,words.weight,words.wordid 
    FROM links 
    JOIN words ON (words.linkid=links.linkid) 
    JOIN domain ON (domain.siteid=links.siteid) 
    WHERE  (words.wordid=271 or words.wordid=8596)
    ORDER BY words.weight DESC LIMIT 0, 8

---

并确保主键上有索引。

不要使用内部查询。还应避免在where子句中使用OR，因为它不使用索引。对wordid、linkid和siteid建立索引，然后尝试以下查询：

SELECT DISTINCT(links.linkid),domain.ip,links.linkid,
links.url,words.weight,words.wordid 
FROM links 
JOIN words ON (words.linkid=links.linkid) 
JOIN domain ON (domain.siteid=links.siteid) 
WHERE words.wordid  IN (271,8596)
ORDER BY words.weight DESC LIMIT 0, 8

试试这个：

SELECT DISTINCT(links.linkid),domain.ip,links.linkid,
links.url,words.weight,words.wordid 
    FROM links 
    JOIN 
    (SELECT linkid,weight,wordid FROM words WHERE wordid IN (271,8596)) words 
      ON (words.linkid=links.linkid) 
    JOIN domain 
      ON (domain.siteid=links.siteid) 
ORDER BY words.weight DESC LIMIT 0, 8;

可能重复的