SQL选择字段“A”为唯一的所有列

Question

我正在使用Java Spring JPA框架，我有下表：

+----+---------+-----------+
| id | userID  | creditID  |
+----+---------+-----------+
|  1 | 1       | 1         |
|  2 | 1       | 2         |
|  3 | 1       | 3         |
|  4 | 2       | 4         |
|  5 | 1       | 1         |
|  6 | 1       | 2         |
+----+---------+-----------+

我想根据userID进行查询，以获取最新且唯一的creditIDs。我最近尝试过查询"SELECT * FROM Table WHERE user_id = 'userId' GROUP BY credit_id"，因为我的runtime errors语句，我得到了group by。

实现以下结果的最简单的语法是什么？

+----+---------+-----------+
| id | userID  | creditID  |
+----+---------+-----------+
|  3 | 1       | 3         |
|  5 | 1       | 1         |
|  6 | 1       | 2         |
+----+---------+-----------+

Answer 1

您的问题的解决方案

  SELECT id, user_id, distinct(creditID) FROM Table WHERE user_id = 1

Answer 2

使用select并过滤where：

select t.*
from t
where t.id = (select max(t2.id) from t t2 where t2.userid = t.userid and t2.creditid = t.creditid) and
      t.userid = 1;

Answer 3

SELECT id, userid, DISTINCT(creditid) FROM table WHERE userid = 'required user id';