SQL查詢不會在加入

Question

每個匹配項返回多個行我有2個表：

mysql> describe solution_sections; 
+---------------------+---------------+------+-----+---------+----------------+ 
| Field    | Type   | Null | Key | Default | Extra   | 
+---------------------+---------------+------+-----+---------+----------------+ 
| solution_section_id | int(10)  | NO | PRI | NULL | auto_increment | 
| display_order  | int(10)  | NO |  | NULL |    | 
| section_name  | varchar(1000) | YES |  | NULL |    | 
+---------------------+---------------+------+-----+---------+----------------+ 
3 rows in set (0.00 sec) 

mysql> describe suggested_solution_comments; 

+-----------------------+----------------+------+-----+---------+----------------+ 
| Field     | Type   | Null | Key | Default | Extra   | 
+-----------------------+----------------+------+-----+---------+----------------+ 
| comment_id   | int(10)  | NO | PRI | NULL | auto_increment | 
| problem_id   | int(10)  | NO |  | NULL |    | 
| suggested_solution_id | int(10)  | NO |  | NULL |    | 
| commenter_id   | int(10)  | NO |  | NULL |    | 
| comment    | varchar(10000) | YES |  | NULL |    | 
| solution_part   | int(3)   | NO |  | NULL |    | 
| date     | date   | NO |  | NULL |    | 
+-----------------------+----------------+------+-----+---------+----------------+ 

我所試圖做的是顯示從solution_sections表SECTION_NAME的名單，和n匹配來自suggested_solution_comments表中每個section_name的項目。因此，對於每個部分名稱，查詢都應該獲得與其關聯的suggested_solution_comments列表。

該表由suggested_solution_comments.solution_part鏈接和solution_sections.solution_section_id

這裏是我試圖至今：

select section_name , comment , solution_part , display_order from solution_sections 
    left join suggested_solution_comments on 
    solution_sections.solution_section_id = suggested_solution_comments.solution_part 
    where suggested_solution_id = 188 OR suggested_solution_id IS NULL 
    group by display_order; 

的問題是，查詢獲取SECTION_NAME的列表，以及一個每個section_name匹配評論，但不多於一條評論。任何想法爲什麼它沒有得到所有相關的評論？

謝謝！

Answer 1

的GROUP BY可以解釋你所看到的嘗試沒有它（UPDATE按照評論）

select section_name , comment , solution_part , display_order 
from solution_sections 
left join suggested_solution_comments on 
solution_sections.solution_section_id = suggested_solution_comments.solution_part 
where suggested_solution_id = 188 OR suggested_solution_id IS NULL 
order by display_order; 

一些言論：

您的數據模型，似乎有點怪......例如solution_part是int(3)且鏈接到solution_section_id即將出現autoincrement int(10)？