Question

我有一个如下所示的表结构，我希望能够检索每个公司代码具有最高值的前三个记录。

我用Google搜索，我找不到更好的方式，所以希望你们能帮助我。

顺便说一句，我在MySQL和SAP HANA中尝试这种方式。但我希望如果能够获得只有MySQL的帮助，我可以获取“HANA”的“结构”

非常感谢！

这是表格：

http://pastebin.com/xgzCgpKL

Answer 1

在MySQL中你可以做到

无论是否模仿ROW_NUMBER()分析函数，每组（公司）都可以获得三个记录。具有相同值的记录获得相同的排名。

SELECT company, plant, value
  FROM
(
  SELECT company, plant, value, @n := IF(@g = company, @n + 1, 1) rnum, @g := company
    FROM table1 CROSS JOIN (SELECT @n := 0, @g := NULL) i
   ORDER BY company, value DESC, plant
) q
 WHERE rnum <= 3;

输出：

| COMPANY | PLANT | VALUE |
|---------|-------|-------|
|       1 |     C |     5 |
|       1 |     B |     4 |
|       1 |     A |     3 |
|       2 |     G |     6 |
|       2 |     C |     5 |
|       2 |     D |     3 |
|       3 |     E |     8 |
|       3 |     A |     7 |
|       3 |     B |     3 |

获取每个组的所有记录，其排名为1到3，模拟DENSE_RANK()分析函数

SELECT company, plant, value
  FROM
(
  SELECT company, plant, value, @n := IF(@g = company, IF(@v = value, @n, @n + 1), 1) rnum, @g := company, @v := value
    FROM table1 CROSS JOIN (SELECT @n := 0, @g := NULL, @v := NULL) i
   ORDER BY company, value DESC, plant
) q
 WHERE rnum <= 3;

输出：

| COMPANY | PLANT | VALUE |
|---------|-------|-------|
|       1 |     C |     5 |
|       1 |     B |     4 |
|       1 |     A |     3 |
|       1 |     E |     3 |
|       1 |     G |     3 |
|       2 |     G |     6 |
|       2 |     C |     5 |
|       2 |     D |     3 |
|       3 |     E |     8 |
|       3 |     A |     7 |
|       3 |     B |     3 |
|       3 |     G |     3 |

这是 SQLFiddle 演示

更新现在它看起来像HANA supports analytic functions所以查询看起来像

SELECT company, plant, value
  FROM
(
  SELECT company, plant, value, 
         ROW_NUMBER() OVER (PARTITION BY company ORDER BY value DESC) rnum
    FROM table1
) 
 WHERE rnum <= 3;

SELECT company, plant, value
  FROM
(
  SELECT company, plant, value, 
         DENSE_RANK() OVER (PARTITION BY company ORDER BY value DESC) rank
    FROM table1
) 
 WHERE rank <= 3;

以下是 SQLFiddle 演示适用于Oracle，但我相信它也适用于HANA

限制特定列sql的输出hana

1 个答案: