MySQL 可选的 LEFT JOIN With MATCH

Question

我有以下查询，它针对 MySQL Innodb 数据库中的相同搜索词对两个不同表中的两列执行全文搜索；

SELECT Id, 
MATCH (tb1.comment, tb2.comment) AGAINST (+'search term' IN BOOLEAN MODE) AS Relevance
FROM tbl1
LEFT JOIN tb2 ON tb1.Id = tb2.Id
WHERE MATCH (tb1.comment, tb2.comment) AGAINST (+'search term' IN BOOLEAN MODE) 
HAVING Relevance > 0 

如果我只对 tb1.comment 执行 MATCH，它工作正常并且我得到相关的搜索词，但我想对两个列执行它。

然而，因为另一个表对于 LEFT JOIN 是可选的，所以如果没有匹配的 ID，它不会返回任何内容。关于如何克服这个问题的任何想法？

Answer 1

我设法找出了以下似乎表现良好并给出我想要的结果的变通方法；

    SELECT Id, 
    MATCH (tb1.comment) AGAINST (+'search term' IN BOOLEAN MODE) AS Relevance1,
    MATCH (tb2.comment) AGAINST (+'search term' IN BOOLEAN MODE) AS Relevance2
    FROM tbl1
    LEFT JOIN tb2 ON tb1.Id = tb2.Id
    WHERE (MATCH (tb1.comment) AGAINST (+'search term' IN BOOLEAN MODE) 
    OR MATCH ( tb2.comment) AGAINST (+'search term' IN BOOLEAN MODE))
    HAVING (Relevance1+Relevance2) > 0 
    ORDER BY (Relevance1+Relevance2) DESC