Question

我需要获取n个不同发票编号的行。

我有SELECT查询，该查询为我提供了来自表的结果：

SELECT A.INVOICE_NUMBER, A.INVOICE_SEQ_NUMBER, B.FILE_NUMBER 
FROM TABLE1 AS A, TABLE2 AS B 
WHERE A.INVOICE_NUMBER = B.INVOICE_NUMBER 
      AND A.INVOICE_SEQ_NUMBER = B.INVOICE_SEQ_NUMBER

所以我的查询结果是这样的：

-----------------------------------------------------
| INVOICE_NUMBER | INVOICE_SEQ_NUMBER | FILE_NUMBER |
------------------------------------------------------
|1111111111-1    |          1         | P4324324525 |
-----------------------------------------------------
|1111111111-1    |          2         | P4565674574 |
-----------------------------------------------------
|1111111111-1    |          3         | V4324552557 |
-----------------------------------------------------
|1111111111-1    |          4         | V4324552525 |
-----------------------------------------------------
|2222222222-2    |          1         | S4563636574 |
-----------------------------------------------------
|3333333333-3    |          1         | Q4324325675 |
-----------------------------------------------------
|3333333333-3    |          2         | Q4565674574 |
-----------------------------------------------------
|4444444444-4    |          1         | F4326364366 |
-----------------------------------------------------
|4444444444-4    |          2         | F4565636323 |
-----------------------------------------------------
|4444444444-4    |          3         | F4398798588 |
-----------------------------------------------------
|4444444444-4    |          4         | F4565865888 |
-----------------------------------------------------

但是例如，我需要的是仅获取三个不同发票编号的结果，因此我的查询应给出以下内容：

-----------------------------------------------------
| INVOICE_NUMBER | INVOICE_SEQ_NUMBER | FILE_NUMBER |
------------------------------------------------------
|1111111111-1    |          1         | P4324324525 |
-----------------------------------------------------
|1111111111-1    |          2         | P4565674574 |
-----------------------------------------------------
|1111111111-1    |          3         | V4324552557 |
-----------------------------------------------------
|1111111111-1    |          4         | V4324552525 |
-----------------------------------------------------
|2222222222-2    |          1         | S4563636574 |
-----------------------------------------------------
|3333333333-3    |          1         | Q4324325675 |
-----------------------------------------------------
|3333333333-3    |          2         | Q4565674574 |
-----------------------------------------------------

我该如何实现？

Answer 1

您听说过JOIN吗？

无论如何，一种解决问题的方法是使用DENSE_RANK()：

SELECT INVOICE_NUMBER, INVOICE_SEQ_NUMBER, FILE_NUMBER
FROM (SELECT A.INVOICE_NUMBER, A.INVOICE_SEQ_NUMBER, B.FILE_NUMBER,
             DENSE_RANK() OVER (ORDER BY A.INVOICE_NUMBER) as seqnum
      FROM TABLE1 A JOIN
           TABLE2 B 
           ON A.INVOICE_NUMBER = B.INVOICE_NUMBER AND 
              A.INVOICE_SEQ_NUMBER = B.INVOICE_SEQ_NUMBER
     ) t
WHERE seqnum <= 3;

如何获取列的n个不同值的行

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