Question

我正在尝试创建一个视图来输出用户朋友的所有帖子。问题是我得到帖子的重复输出。正如您在视图中看到的那样，我得到2行同一帖子。有没有办法将列user1和user2分组为这样的帖子

post   
  user1 user2   
  user1 user2

而不是像目前正在做的那样

post user1 user2
post user1 user2

下面是我的表结构

+----------------------------------------------+
|                     posts                    | 
+----+------+--------+--------+------+---------+
| id | post | postBy | postTo | date | deleted |
+----+------+--------+--------+------+---------+
| 1  | text | 1      | 0      | date | 0       |
+----+------+--------+--------+------+---------+

+---------------------------+
|          friends          |
+----+-------+-------+------+
| id | user1 | user2 | date |
+----+-------+-------+------+
| 1  | 1     | 2     | date |
| 2  | 1     | 3     | date |
+----+-------+-------+------+

CREATE VIEW posts_by_friend AS SELECT posts.id, posts.post, posts.postBy, posts.postTo, posts.date, posts.deleted, friends.user1, friends.user2 FROM posts 
INNER JOIN friends ON (posts.postBy = friends.user1 OR posts.postBy = friends.user2) GROUP BY posts.id, friends.user1, friends.user2

+--------------------------------------------------------------+
|                       posts_by_friend                        | 
+----+------+--------+--------+------+---------+-------+-------+
| id | post | postBy | postTo | date | deleted | user1 | user2 |
+----+------+--------+--------+------+---------+-------|-------|
| 1  | text | 1      | 0      | date | 0       | 1     | 2     |
| 1  | text | 1      | 0      | date | 0       | 1     | 3     |
+----+------+--------+--------+------+---------+-------+-------+

$userId = 1;

SELECT * FROM `posts_by_friend` WHERE `deleted`=0 AND (`user1`='$userId' or `user2`='$userId'));

Answer 1

您可以通过在user1和user2上应用group_concat来获得预期的输出（不同的帖子）

CREATE VIEW posts_by_friend AS 
SELECT p.id, p.post, p.postBy, p.postTo, p.date, p.deleted, group_concat(f.user1) user1, group_concat(f.user2) user2 
FROM posts p
INNER JOIN friends f ON (p.postBy = f.user1 OR p.postBy = f.user2) 
GROUP BY  p.id, p.post, p.postBy, p.postTo, p.date, p.deleted

在我的MySQL视图中获取重复的行

1 个答案: