Question

我有一个SQL select查询生成的以下数据。数据首先按ID递增，然后按AVO降序排列，如下所示：

+-------+----------------+------+-------+---------+----------+-----+
|  ID   |      Link      | Name | Type  | Subtype | Domicile | AVO |
+-------+----------------+------+-------+---------+----------+-----+
| 11111 | www.aaaaa3.com | AAAA | FUND  | 40 act  | USA      | 456 |
| 11111 | www.aaaaa2.com | AAAA | FUND  | 40 act  | USA      | 456 |
| 11111 | www.aaaaa6.com | AAAA | FUND  | 40 act  | UK       | 345 |
| 11111 | www.aaaaa1.com | AAAA | FUND  | 40 act  | USA      | 123 |
| 11111 | www.aaaaa4.com | AAAA | FUND  | 40 act  | USA      |     |
| 11111 | www.aaaaa5.com | AAAA | FUND  | 40 act  | USA      |     |
| 22222 | www.bbbb1.com  | BBBB | BANK  | Inv     | Canada   | 897 |
| 22222 | www.bbbb5.com  | BBBB | BANK  | Inv     | Brazil   | 586 |
| 22222 | www.bbbb3.com  | BBBB | BANK  | Inv     | Cayman   | 357 |
| 22222 | www.bbbb2com   | BBBB | BANK  | Inv     | Cayman   |     |
| 22222 | www.bbbb4.com  | BBBB | BANK  | Inv     | Cayman   |     |
+-------+----------------+------+-------+---------+----------+-----+

我需要做的是每个ID只保留一行，每个ID的字段AVO中的值最大，并删除其他ID。如果任何给定ID存在AVO字段中的两个相同值（请参见上表中的前两行），则保留第一行并删除另一行。

我想我可以在VBA中为每个ID值使用For ... Next循环，但我宁愿在SQL中运行它。这甚至可能吗？是否可以在Access中的SQL删除查询中嵌套循环？

感谢您的协助。

Answer 1

假设您已添加名为AN的自动编号字段，则可以使用以下查询：

DELETE * FROM MyTable
WHERE AN NOT IN(
    SELECT AN From (MyTable t1
    INNER JOIN (SELECT Max(AN) AS MaxAN, ID, AVO  FROM MyTable GROUP BY ID, AVO) t2 ON t1.AN = t2.MaxAN)
    INNER JOIN (SELECT ID, Max(AVO) As MaxAVO FROM MyTable GROUP BY ID) t3 ON (t2.ID = t3.ID AND t2.AVO = t3.MaxAVO)
)

使用SQL在MS Access中删除循环？

1 个答案: