SQL内部联接错误结果

Question

我的问题如下：

我正在尝试使用WordNet MySQL，除了已经存在的视图外，试图添加另一个视图，例如：

CREATE OR REPLACE VIEW synsetsXsemlinksXsynsets AS 
SELECT 
       linkid,s.synsetid AS ssynsetid
       ,s.definition AS sdefinition
       ,d.synsetid AS dsynsetid
       ,d.definition AS ddefinition 
FROM synsets AS s 
     INNER JOIN 
     semlinks AS l ON s.synsetid = l.synset1id 
     INNER JOIN 
     synsets AS d ON l.synset2id = d.synsetid;

所以以该代码为参考，我试图做类似的事情：

CREATE VIEW graph AS  
SELECT 
       l.linkid
       ,s.synsetid AS sssinsetid
       ,w.lemma AS swlemma
       ,s.definition AS sdefinition
       ,d.synsetid AS dsynsetid
       ,w.lemma AS dwlemma
       ,d.definition AS ddefinition 
FROM synsets AS s 
     INNER JOIN  
     semlinks AS l ON s.synsetid = l.synset1id 
     INNER JOIN  
     synsets AS d ON l.synset2id = d.synsetid 
     INNER JOIN  
     lexlinks AS x ON l.synset1id = x.synset1id 
                      AND l.synset2id = x.synset2id 
     INNER JOIN  
     words AS w ON w.wordid = x.word1id 
                      AND x.word2id = w.wordid

为了得到：linkid | ssynsetid | swlemma | sdefition| dsynsetid | dwlemma | ddefition。

但是它没有按预期工作。第一个给我285639行，而我的给我12行。我不确定问题出在哪里。有帮助吗？

Answer 1

将LEFT JOIN用于2个额外的表。

 ...
 FROM synsets AS s 
 INNER JOIN  
 semlinks AS l ON s.synsetid = l.synset1id 
 INNER JOIN  
 synsets AS d ON l.synset2id = d.synsetid 
 LEFT JOIN  
 lexlinks AS x ON l.synset1id = x.synset1id 
                  AND l.synset2id = x.synset2id 
 LEFT JOIN  
 words AS w ON w.wordid = x.word1id 
                  AND x.word2id = w.wordid

因为如果使用INNER JOIN，那么它将过滤不匹配的那些。