[英]SQL - Generate Round robin number on insert
我正在部署一個現有的定制 Windows 服務 (C#) 多個實例,這些實例將從單個隊列表中讀取。
隊列基於以下簡單的 SQL 表。
Record-Id (int auto id)
Added-Date (Date)
Added-By (Text)
Data-To-be-Processed (Text)
**Pool-Number (int)**
給定最大池大小,如何為每個插入創建循環序列號? 這里我使用的池大小為 3(這可以硬編碼)。 例如
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
我曾考慮使用序列表並在每次插入時將其遞增,並在達到最大池大小時將其重置為 1,例如
TbSeq
dbSeq (int) (Will contain 1-3 depending last insert)
有一個更好的方法嗎?
如果您可以使用RecordId
作為輔助,那么您可以使用Modulo ( %
)
select *, 1+((RecordId-1)%3) as Pool
from t
reextester 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 |
+----------+------------+-------------------+------+
您可以將其添加為計算列(持久化可選,但推薦)
alter table t
add Pool as (1+((RecordId-1)%3)) persisted;
我不會依賴RecordId
本身。 它可能有間隙。 進行真正循環的最簡單方法是使用row_number()
和模運算:
select 1 + (row_number() over (order by id) - 1) % 3 as poolnum
from t;
如果您知道RecordId
沒有間隙,那么您可以改用它。 使用RecordId
效率更高,因為您可以在一行內進行完整計算,甚至可以添加一個計算列:
alter table t add poolnum as (1 + (row_number() over (order by id) - 1) % 3)
您可以將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;
結果:
+-----------+---------------------+----------+----------------------+-------------+
| 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 |
+-----------+---------------------+----------+----------------------+-------------+
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