我有一个包含以下两个表的数据库,用户,帖子我正在寻找一种方法来获取用户拥有多少帖子(postCount)的计数,并且如果用户没有任何帖子,则 postCount 将等于零
Users Posts
+----+------+ +----+---------+-----------+
| ID | Name | | ID | user_id | Name |
+----+------+ +----+---------+-----------+
| 1 | Bob | | 1 | 1 | Blargg... |
| 2 | Jim | | 2 | 1 | Blargg... |
| 3 | Jo | | 3 | 2 | Blargg... |
+----+------+ +----+---------+-----------+
Run Code Online (Sandbox Code Playgroud)
最后我想要这样的东西:
+----+------+
| ID | Count|
+----+------+
| 1 | 2 |
| 2 | 1 |
| 3 | 0 |
+----+------+
Run Code Online (Sandbox Code Playgroud)
尝试这个:
SELECT u.ID, u.Name, COUNT(p.Name)
FROM Users AS u
LEFT JOIN Posts AS p ON u.ID = p.user_id
GROUP BY u.ID, u.Name
Run Code Online (Sandbox Code Playgroud)