如何使用两个内部加入

Question

使用此查询来获取与履行所有三项必需的词项（联想，笔记本电脑，计算机）字样的产品优化查询：

SELECT t1.id, t1.name, t1.price FROM 
(SELECT p.id AS productid, name, price 
FROM products p JOIN productwords pw ON p.id = pw.productid 
JOIN words w ON pw.wordid = w.id WHERE word.term = 'lenovo') t1 
INNER JOIN 
(SELECT p.id AS productid, name, price 
FROM products p JOIN productwords pw ON p.id = pw.productid 
JOIN words w ON pw.wordid = w.id WHERE word.term = 'laptop') t2 
INNER JOIN 
(SELECT p.id AS productid, name, price 
FROM products p JOIN productwords pw ON p.id = pw.productid 
JOIN words w ON pw.wordid = w.id WHERE word.term = 'computer') t3 
ON 
t1.productid = t2.productid 
AND 
t1.productid = t3.productid 
ORDER BY t1.name 

据我所看到的，查询考虑每个术语的整个单词表（这些表具有索引，数据库是MySql）。

查询是否可以以更好的方式重写，所以它会变得更快？ （这些表格包含数百万行）

例如，对于子集，因此'笔记本电脑'搜索仅考虑与'lenovo'匹配的行 - 而'计算机'搜索仅考虑匹配第一个'lenovo'的行，然后'笔记本电脑'。

谢谢！

Answer 1

可以使用HAVING条款：

SELECT p.id AS productid, name, price 
FROM products p 
JOIN productwords pw ON p.id = pw.productid 
JOIN words w ON pw.wordid = w.id 
WHERE word.term in ('lenovo','computer','laptop') 
GROUP BY p.id , name, price 
HAVING COUNT(DISTINCT word.term) = 3 

也就是说，如果我的理解这个问题，它看起来像产品 - >话是1：N的关系，如果没有选择从word表列，这应该是完美的。

Answer 2

这可能是做的更快捷的方法：

SELECT p.id, name, price FROM products p where EXISTS (select null from productwords pw1 JOIN words w1 ON pw1.wordid = w1.id where w1.term = 'lenovo' and p.id = pw1.productid) and EXISTS (select null productwords pw2 JOIN words w2 ON pw2.wordid = w2.id where w2.term = 'laptop' and and p.id = pw2.productid) and EXISTS (select null productwords pw3 ON p.id = pw3.productid JOIN words w3 where w3.term = 'computer' and p.id = pw3.productid)
ORDER BY name;