如何查询获取仅显示在其他表上有一个字段的关系id的位置。我的解释表是:
In Table Users+--------+------------+
| id | username |
+--------+------------+
| 1 |zuck |
| 2 |renold |
| 3 |arby |
| | |
In Table Class
+--------+------------+------------+
| id | user_id | class_name |
+--------+------------+------------+
| 1 | 1 | ABC |
| 2 | 1 | EFG |
| 3 | 1 | HIJ |
| 4 | 2 | KLM |
| 5 | 2 | NOP |
和我想得到的结果如下:
Array
(
[0] => Array
(
[id] => 1
[username] => zuck
[class] => Array
(
[0] => array(
[id] => 1
[class_name] => ABC
)
[1] => array(
[id] => 2
[class_name] => EFG
)
[2] => array(
[id] => 3
[class_name] => HIJ
)
)
)
[1] => Array
(
[id] => 2
[username] => renold
[class] => Array
(
[0] => array(
[id] => 4
[class_name] => KLM
)
[1] => array(
[id] => 5
[class_name] => NOP
)
)
)
)
所以username arby没有显示,因为他在表类中没有关系。在表类中没有user_id 3。因此将只显示用户zuck和renold。我尝试查询左连接,外连接,内连接,但不成功:-(
)SELECT Users.username,Class.class_name FROM Users INNER JOIN Class ON Users.id = Class.user_id;