Question

我有4张桌子：

ad
image
placement
ad_placement - many to many intermediary table between ad and placement

图片有广告FK

结构是这样的：

ad

id | url

1   http://
2   http://
3   http:// 


placement

id | name

1    name_1
1    name_2


ad_placement

id | ad_id | PLACEMENT_ID 1 1 1 2 1 2 3 2 2

image

id  | image    | ad_id 
1     http://    1
2     http://    2
3     http://    3

我想获取广告中的字段，网址和图片中的图片，其中placement = name_1

＆＃39; **＆＃39;在查询中只显示我所指的

  SELECT A.id, A.url, I.image as image 
  FROM ad AS A LEFT JOIN (       
  SELECT ADP.ad_id FROM ad_placement *AS ADP*
  JOIN placement AS P ON ADP.placement_id = P.id **WHERE P.name='name_1'**) AS AP ON A.id=AP.ad_id  
  LEFT JOIN ( SELECT ad_id,image FROM image) AS I ON I.ad_id = A.id 
  WHERE A.is_active=TRUE

当我尝试在此行使用where时出现错误

JOIN ads_adplacement AS P ON ADP.adplacement_id = P.id WHE...

missing FROM-clause entry for table "adp"

删除＆＃39;哪里＆＃39;有效，但不是我需要的

我按建议添加了ADP（用斜体看**）我得到相同的结果，比如忽略where子句

Answer 1

第一次左加入有什么意义？

SELECT A.id, A.url, I.image as image 
  FROM ad AS A 
  LEFT JOIN image AS I ON I.ad_id = A.id 
  WHERE A.is_active=TRUE

编辑：可能你的意思是这个。

SELECT A.id, A.url, I.image as image 
  FROM ad AS A 
  LEFT JOIN image AS I ON I.ad_id = A.id 
  WHERE A.is_active=TRUE and
  a.id in 
  (select ad_id 
   from ad_placement adp 
   inner join placement p on p.Id = adp.placement_id 
   where p.Name='name 1');

Answer 2

请您分享完整的查询，我想看看您在哪里添加where子句。但是，似乎您要添加两个连接之间的位置。加入所有表后可以添加的位置。

修改

SELECT A.id, A.url, I.image as image 
FROM ad AS A 
LEFT JOIN ad_placement AS AP ON A.id=AP.ad_id
LEFT JOIN placement AS P ON AP.placement_id = P.id
LEFT JOIN image I ON I.ad_id = A.id 
WHERE A.is_active=TRUE and P.name='name_1'

多个join子句使用suqbqueries，其中有多个where

2 个答案: