從表格中獲取所有記錄，並從其他表格中獲取與其相關的信息

Question

我有三張表格（學生，團體，主題）和另外兩張表格作爲橋樑（弱）表格來連接學生與另外兩張表格（students_groups，students_subjects）.something LIK這樣的：

+-----+----------------+  +-----+-----------+ +-----+-----------+ 
| id | student_name |  | id |group_name | | id |course_name| 
+-----|---------+------|  +-----|-----------+ +-----|-----------+ 
| 1 | stunet 1  |  |1 | g1  | |1 | c1  | 
| 2 | stuent 2  |  |2 | g2  | |2 | c2  | 
| 3 | stuent 3  |  |3 |   | |3 |   | 
+-----+---------+------+  +-----+-----------+ +-----+-----------+ 

    +------------+-----------+  +------------+------------+ 
    | student_id | group_id |  | stuent_id | course_id | 
    +------------+-----------+  +------------+------------+ 
    | 1   | 1  |  | 1   | 2   | 
    | 2   | 2  |  | 3   | 1   | 
    |   |   |  +------------+------------+ 
    +------------+-----------+ 

我想要的是：顯示所有學生（它們是否被分配到組或不，它們是否被registerd的科目或不）的主題和組。

+-----+---------+-----------+ 
| student | group | deleted | 
+---------|-------+---------| 
|student 1| g1 |c2  | 
|student 2| g2 |   | 
|student 3|  |c1  | 
+---------+-------+---------+ 

我前面的查詢只顯示被分配到一組，並registerd一些主題

 select students.*  
    groups.group_name, 
    modules.module_name 
    from students 
    JOIN students_groups ON students.id = students_groups.student_id 
    JOIN groups ON students_groups.group_id = groups.id 
    JOIN students_modules ON students.id = students_modules.student_id 
    JOIN modules ON students_modules.module_id = groups.id 

+-----+---------+-----------+ 
| student | group | deleted | 
+---------|-------+---------| 
|student 1| g1 |c2  | 
+-----+---------+-----------+ 

Answer 1

使用LEFT OUTER JOIN代替JOIN學生：

Select 
std.studentname, 
grp.groupname, 
crs.coursename 
FROM test.student std 
LEFT OUTER JOIN test.stu_grp_brg sgb 
on sgb.student_id=std.id 
left outer join test.group grp 
on sgb.group_id=grp.id 
left outer join test.stu_course_brg scb 
on scb.student_id=std.id 
left outer join test.course crs 
on crs.id=scb.course_id