使用MySQL多對多select語句查找相對行

Question

我嘗試使用內部連接來查找相對行。

但似乎它什麼都沒有返回。請指教。

基本上，我已經分解了原始頁面標題和每篇文章的描述中的所有關鍵字。所以，當我來搜索時，我可以查詢關鍵字表。

這裏是關鍵字

一個文章 - 表模式

CREATE TABLE article   (id INT, title TEXT, description TEXT); 
CREATE TABLE keyword   (id INT, keyword VARCHAR(255)); 
CREATE TABLE article_keyword (article_id INT, keyword_id INT); 

- 添加第1條

insert into article set 
id = 1, 
title = "my text book like a black hole", 
description = "I have a text book. Any people who read it and after days they will disappear. etc..."; 

- 添加關鍵字的第1條

insert into keyword set 
id = 1, 
keyword = "text book"; 

insert into keyword set 
id = 2, 
keyword = "black hole"; 

insert into article_keyword set 
article_id = 1, 
keyword_id = 1; 

insert into article_keyword set 
article_id = 1, 
keyword_id = 2; 

- 添加第2條

insert into article set 
id = 2, 
title = "the fact of deep space black hole", 
description = "More researches are telling fake story about black holes is exists. But my alien friend tell me it is wrong ... etc"; 

- 添加關鍵字以第2條

insert into keyword set 
id = 3, 
keyword = "research"; 

insert into keyword set 
id = 4, 
keyword = "alien"; 

insert into article_keyword set 
article_id = 2, 
keyword_id = 2; 

insert into article_keyword set 
article_id = 2, 
keyword_id = 3; 

insert into article_keyword set 
article_id = 2, 
keyword_id = 4; 

- 使用 「教科書」 查找，預計1篇

SELECT article.id, title FROM article 
JOIN article_keyword ak ON ak.article_id = article.id 
JOIN keyword k1   ON ak.keyword_id = k1.id 
WHERE k1.keyword = "text book" 

- 用 「黑洞」 調查，預計2篇文章

SELECT article.id, title FROM article 
JOIN article_keyword ak ON ak.article_id = article.id 
JOIN keyword k2   ON ak.keyword_id = k2.id 
WHERE k2.keyword = "black hole" 

- 當搜索博確定包括所有這些關鍵字，然後得不到。

SELECT article.id, title FROM article 
JOIN article_keyword ak ON ak.article_id = article.id 
JOIN keyword k1   ON ak.keyword_id = k1.id 
JOIN keyword k2   ON ak.keyword_id = k2.id 
WHERE k1.keyword = "text book" 
AND k2.keyword = "black hole"; 

任何想法的MySQL無法讓我回到第1條？

這個查詢有什麼問題嗎？

謝謝！

Answer 1

是的，你的查詢是錯誤的，因爲where子句限制article_keyword和關鍵字（K1）之間的連接與關鍵字排第一= 1和的article_id = 1，並沒有行會匹配第二where子句關鍵字2.

如果你想用多個關鍵詞的文章，你可以使用此查詢：

SELECT article.id, title 
FROM article 
JOIN article_keyword ak ON ak.article_id = article.id 
JOIN keyword k   ON ak.keyword_id = k.id 
WHERE k.keyword = "text book" 
OR k.keyword = "black hole" 
GROUP BY article.id, title 
HAVING COUNT(keyword) = 2 

Answer 2

您的第一個2 SELECT聲明工作正常。在最後SELECT聲明使用DISTINCT和WHERE子句嘗試OR而不是AND。

SELECT DISTINCT article.id, title FROM article 
JOIN article_keyword ak ON ak.article_id = article.id 
JOIN keyword k1   ON ak.keyword_id = k1.id 
JOIN keyword k2   ON ak.keyword_id = k2.id 
WHERE k1.keyword = "text book" 
OR k2.keyword = "black hole";