内部连接SQL

Question

Learning_tutors：

Learning_subject：

Learning_subjects：

Learning_level：
Learning_level table

我希望能够根据学习科目表中的subjectID获取教导科目的导师的名字，并将其加入学习科目表，该表格对应于学习中的tutorID导师表

这是我尝试过的

SELECT learning_subjects.levelid, 
       learning_subjects.tutorid, 
       learning_tutor.id, 
       learning_tutor.NAME, 
       learning_level.id 
FROM   learning_subjects 
       INNER JOIN learning_level 
               ON learning_subjects.levelid = learning_level.id 
       INNER JOIN learning_subjects.tutorid 
               ON learning_tutor.id 
WHERE  learning_subjects.tutorid = 1 

Answer 1

select
    s.levelID, t.Name, l.Subject 
from
    Learning_tutors t, Learning_subject l, Learning_subjects s 
where s.tutorID = t.ID AND s.subjectID = l.ID

这为您提供了一种从各种表格中获取信息的灵活方式。

Answer 2

我认为你的第二次加入稍微偏离了

SELECT learning_subjects.levelid, 
       learning_subjects.tutorid, 
       learning_tutor.id, 
       learning_tutor.NAME, 
       learning_level.id 
FROM   learning_subjects 
       INNER JOIN learning_level 
               ON learning_subjects.levelid = learning_level.id 
       **INNER JOIN learning_tutors
               ON learning_tutor.id = learning_subjects.tutorid**
WHERE  learning_subjects.tutorid = 1 

Answer 3

您需要在 INNER JOIN 和 WHERE 子句部分略有变化：

 FROM learning_subjects INNER JOIN learning_level ON learning_subjects.levelid = learning_level.id 
                        INNER JOIN learning_tutor ON learning_subjects.tutorid = learning_tutor.id
 WHERE learning_subjects.subjectID = 1