如何使用兩個內部加入

Question

使用此查詢來獲取與履行所有三項必需的詞項（聯想，筆記本電腦，計算機）字樣的產品優化查詢：

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 

據我所看到的，查詢考慮每個術語的整個單詞表（這些表具有索引，數據庫是MySql）。

查詢是否可以以更好的方式重寫，所以它會變得更快？ （這些表格包含數百萬行）

例如，對於子集，因此'筆記本電腦'搜索僅考慮與'lenovo'匹配的行 - 而'計算機'搜索僅考慮匹配第一個'lenovo'的行，然後'筆記本電腦'。

謝謝！

Answer 1

可以使用HAVING條款：

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 

也就是說，如果我的理解這個問題，它看起來像產品 - >話是1：N的關係，如果沒有選擇從word表列，這應該是完美的。

Answer 2

這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;