我在DB WordPress中安装了2个自定义表，两个表之间具有NULL关系。
这是两个表：
one-to-many如您所见，每个帖子都有一个类别，同时使用 posts table
_________________________________________________________________
| id | title | content | category_id | post_order | post_active |
|____|_______|_________|_____________|_____________|_____________|
| 1 | test1 | testing | 1 | 0 | 1 |
| 2 | test2 | testing | 1 | 1 | 1 |
| 3 | test3 | testing | 2 | 2 | 0 |
| . | ..... | ....... | . | . | . |
|____|_______|_________|_____________|_____________|_____________|
categories table
_____________________________________
| c_id | c_name | c_order | c_active |
|______|________|_________|__________|
| 1 | cat1 | 0 | 1 |
| 2 | cat2 | 1 | 1 |
| 3 | cat3 | 2 | 0 |
| . | ..... | ....... | . |
|______|________|_________|__________|
表的category_id列和posts表的c_id列。
我想显示categories表中具有相关类别的所有数据。
这就是我尝试过的：
posts但是我只在每个活动的global $wpdb;
$results = $wpdb->get_results("SELECT b.c_name, a.id, TRIM(a.title) AS title, a.content
FROM posts a
INNER JOIN categories b ON a.category_id = b.c_id
WHERE a.post_active = '1' AND b.c_active = '1'
ORDER BY b.c_order, a.post_order", OBJECT_K );
print_r($results);
中获得第一篇帖子：
category怎么了？如何解决？
答案 0 :(得分：0)
尝试左联接，然后检查：
全局$ wpdb;
$results = $wpdb->get_results("SELECT b.c_name, a.id, TRIM(a.title) AS title, a.content
FROM posts a
LEFT JOIN categories b ON a.category_id = b.c_id
WHERE a.post_active = '1' AND b.c_active = '1'
ORDER BY b.c_order, a.post_order", OBJECT_K );
print_r($results);