Mysql键连接两个表

Question

我试图连接两个表，但似乎有一个问题，我寻找的输出是有主题的行量。

SELECT *
FROM education AS a
JOIN keys2 AS b USING(`List Idsubjek`)
WHERE `List Idsubjek` IN (52, 54, 55, 67)
AND `studentid` = '$id'

id List Idsubjek  Subject
1  52             Maths
2  53             Geography

id List Idsubjek       studentid school
1  52,53,54,74,0,0,0   15        school name

Answer 1

首先，您应该规范您的数据结构，在keys2和教育表之间有一个连接表。

要使联接与当前数据结构一起工作，请使用MySQL的find_in_set()函数：

SELECT *
FROM education AS a
JOIN keys2 AS b on find_in_set(b.`List Idsubjek`,a.`List Idsubjek`)>0 
WHERE b.`List Idsubjek` IN (52, 54, 55, 67)
AND `studentid` = '$id'