Sql 获取具有最大日期和空日期的ID的不同记录

这是我的表1和表2，我使用左连接。 虽然看起来可以放在一张桌子上。 表1就像一个主列表，其中id不能重复 因此，在表2中，我添加了可以复制id的名称和日期

+----+---------+----------------+
| id | Date    | Name           |
+----+---------+----------------+
| 1  | 5/25/17 | Monica Coleman |
| 1  | 5/26/17 | Kelsi Mines    |
| 2  |         |                |
| 3  | 5/9/17  | Vanessa Heart  |
| 4  | 5/8/17  | Ryan Evans     |
| 4  | 5/10/17 | Sharpay Evans  |
| 5  |         |                |
| 6  |         |                |
| 7  | 5/6/17  | Troy Bolton    |
+----+---------+----------------+

如果我使用这个代码

SELECT P.id, R.DateAdded, R.Name FROM Table1 AS P LEFT JOIN Table2 AS R ON P.id=R.id WHERE ((([R.DateAdded])=(SELECT MAX(DateAdded) FROM R WHERE InventoryID = R.InventoryID)));

。。。然后这些结果表明

+----+---------+----------------+
| id | Date    | Name           |
+----+---------+----------------+
| 1  | 5/26/17 | Kelsi Mines    |
| 3  | 5/9/17  | Vanessa Heart  |
| 4  | 5/10/17 | Sharpay Evans  |
| 7  | 5/6/17  | Troy Bolton    |
+----+---------+----------------+

但我想让声明返回的是

+----+---------+----------------+
| id | Date    | Name           |
+----+---------+----------------+
| 1  | 5/26/17 | Kelsi Mines    |
| 2  |         |                |
| 3  | 5/9/17  | Vanessa Heart  |
| 4  | 5/10/17 | Sharpay Evans  |
| 5  |         |                |
| 6  |         |                |
| 7  | 5/6/17  | Troy Bolton    |
+----+---------+----------------+

---

在大多数数据库中，您会将条件添加到

ON

子句中（或使用

行号（）

。MS Access都不支持这两种情况。因此，请使用子查询：

SELECT P.id, R.DateAdded, R.Name
FROM Table1 AS P LEFT JOIN
     (SELECT R.*
      FROM Table2 AS R
      WHERE R.DateAdded = (SELECT MAX(R2.DateAdded) FROM Table2 R2 WHERE R.InventoryID = R2.InventoryID)
     ) as R
     ON P.id = R.id

---

好的，我得到了我的答案。我使用的是空值

SELECT P.id, R.DateAdded, R.Name FROM Table1 AS P LEFT JOIN Table2 AS R ON P.id=R.id WHERE ((([R.DateAdded])=(SELECT MAX(DateAdded) FROM R WHERE InventoryID = R.InventoryID))) OR R.DateAdded IS NULL;

---

@elaine8s…可能是由于

WHERE

子句中的输入错误。