Question

我创建了两个名为“帖子”的表格，其字段为 id，post_name 和“ post_meta ”，字段为 id， post_id，meta_name，meta_vale ..

然后我插入了一些像这样的值。

邮政表中的

： -

+----+--------------+
| id |  post_name   |
+----+--------------+
| 15 | fsdfsd       |
| 16 | fsdgbfg fsd  |
+----+--------------+

Post_meta表中的

： -

+----+---------+-----------+------------+
| id | post_id | meta_name | meta_value |
+----+---------+-----------+------------+
|  1 |      15 | image     | image1.jpg |
|  2 |      15 | image     | image2.jpg |
|  3 |      16 | image     | image3.jpg |
|  4 |      15 | image     | image4.jpg |
+----+---------+-----------+------------+

我想创建一个查询以获得像这样的输出

+----+-------------+-------------+
| id |  post_name  | meta_value  |
+----+-------------+-------------+
| 15 | fsdfsd      | image1.jpg  |
| 16 | fsdgbfg fsd | image3.jpg  |
+----+-------------+-------------+

只有一个meta vale和它的post_id ......

请帮帮我。

Answer 1

select m.id, p.post_name, m.meta_value
from posts p
inner join post_meta m on p.id = m.post_id
inner join 
(
   select post_id, min(id) as minid
   from post_meta
   group by post_id
) m2 on m.post_id = m2.post_id and m.id = m2.minid

Answer 2

SELECT a.id,a.post_name,b.meta_value 
   FROM posts as a 
   INNER JOIN post_meta a p ON a.id=b.post_id

Answer 3

Select * from Post_meta, Post where 
(conditions)
Join Post_meta on Post_meta.Post_id = Post.id

Answer 4

这应该这样做：

SELECT pm.id, p.post_name, pm.meta_value
FROM posts p
INNER JOIN post_meta pm ON pm.post_id = p.id
ORDER BY pm.id ASC
GROUP BY pm.post_id

如何通过相同的条件值从另一个表连接值

4 个答案: