Question

我正在部署一个现有的定制Windows服务（C＃）多个实例，这些实例将从单个队列表中读取。

队列基于以下简单的SQL表。

Record-Id (int auto id)

Added-Date (Date)

Added-By (Text)

Data-To-be-Processed (Text)

**Pool-Number (int)**

如果给定最大池大小，我如何为每个插入创建一个循环序列号？这里我使用的池大小为3（这可以是硬编码的）。 e.g。

1 | 31/10/2014 | DATA | Pool 1

2 | 31/10/2014 | DATA | Pool 2

3 | 31/10/2014 | DATA | Pool 3

4 | 31/10/2014 | DATA | Pool 1

5 | 31/10/2014 | DATA | Pool 2

6 | 31/10/2014 | DATA | Pool 3

7 | 31/10/2014 | DATA | Pool 1

我考虑过使用一个Sequence表并在每个插件上递增它，并在达到最大池大小时将其重置为1。

TbSeq

  dbSeq (int) (Will contain 1-3 depending last insert)

有更好的方法吗？

Answer 1

如果您可以使用RecordId作为辅助，那么您可以使用Modulo (%)

select *, 1+((RecordId-1)%3) as Pool
from t

rextester演示：http://rextester.com/WNEIQM50851

返回：

+----------+------------+-------------------+------+
| RecordId | AddedDate  | DataToBeProcessed | Pool |
+----------+------------+-------------------+------+
|        1 | 2014-10-31 | DATA              |    1 |
|        2 | 2014-10-31 | DATA              |    2 |
|        3 | 2014-10-31 | DATA              |    3 |
|        4 | 2014-10-31 | DATA              |    1 |
|        5 | 2014-10-31 | DATA              |    2 |
|        6 | 2014-10-31 | DATA              |    3 |
|        7 | 2014-10-31 | DATA              |    1 |
+----------+------------+-------------------+------+

您可以将其添加为计算列（持久可选，但建议使用）

alter table t
  add Pool as (1+((RecordId-1)%3)) persisted;

Answer 2

我不会依赖RecordId 本身。它可能有差距。进行真正循环的最简单方法是使用row_number()和模运算：

select 1 + (row_number() over (order by id) - 1) % 3 as poolnum
from t;

如果您知道RecordId没有间隙，那么您可以使用它。使用RecordId更有效，因为您可以在一行内完成全部计算，甚至可以添加计算列：

alter table t add poolnum as (1 + (row_number() over (order by id) - 1) % 3)

Answer 3

您可以将SECQUENCE用作：

CREATE TABLE MyTable (
    Record_Id INT IDENTITY(1,1), Added_Date DATE,
    Added_By VARCHAR(50), Data_To_be_Processed VARCHAR(50), Pool_Number INT);
GO    
CREATE SEQUENCE Pool
AS INT
START WITH 1
MINVALUE 1
MAXVALUE 3
CYCLE
GO

INSERT INTO MyTable VALUES
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool),
('2014-10-31', 'DATA', 'Pool', NEXT VALUE FOR Pool);

SELECT *
FROM MyTable;

结果：

+-----------+---------------------+----------+----------------------+-------------+
| Record_Id |     Added_Date      | Added_By | Data_To_be_Processed | Pool_Number |
+-----------+---------------------+----------+----------------------+-------------+
|         1 | 31.10.2014 00:00:00 | DATA     | Pool                 |           1 |
|         2 | 31.10.2014 00:00:00 | DATA     | Pool                 |           2 |
|         3 | 31.10.2014 00:00:00 | DATA     | Pool                 |           3 |
|         4 | 31.10.2014 00:00:00 | DATA     | Pool                 |           1 |
|         5 | 31.10.2014 00:00:00 | DATA     | Pool                 |           2 |
|         6 | 31.10.2014 00:00:00 | DATA     | Pool                 |           3 |
|         7 | 31.10.2014 00:00:00 | DATA     | Pool                 |           1 |
|         8 | 31.10.2014 00:00:00 | DATA     | Pool                 |           2 |
|         9 | 31.10.2014 00:00:00 | DATA     | Pool                 |           3 |
+-----------+---------------------+----------+----------------------+-------------+

SQL - 在插入时生成循环编号

3 个答案: