[英]How to get ROW_NUMBER to start over (reset) after ROW_NUMBER reaches a certain number
如果每个taskName最多包含3个,我需要ROW_NUMBER列重新开始。 可以有多个具有相同名称的任务,因此,如果有三个以上具有相同名称的任务,则需要ROW_NUMBER列重新开始。
出现新的任务名称后,下面的代码仅让我的ROW_NUMBER列重置,但是,如果数量增加到3,并且仍然存在相同名称的另一个任务,则我需要这样做并将ROW_NUMBER列重置为一个。
SELECT t.[taskId], tq.name as taskName,
ROW_NUMBER() OVER(PARTITION BY tq.name
ORDER BY tq.name) AS RowNum
FROM Task t (NOLOCK)
order by tq.name asc
当前结果:
taskID taskName RowNum
1 Name1 1
2 Name1 2
3 Name1 3
4 Name1 4
5 Name1 5
6 Name1 6
8 Name2 1
8 Name2 2
预期成绩:
taskID taskName RowNum
1 Name1 1
2 Name1 2
3 Name1 3
4 Name1 1
5 Name1 2
6 Name1 3
8 Name2 1
8 Name2 2
使用取模算法:
SELECT t.[taskId], tq.name as taskName,
1 + (ROW_NUMBER() OVER (PARTITION BY tq.name ORDER BY tq.name) - 1) % 3 AS RowNum_3
FROM Task t
ORDER BY tq.name asc;
假设数据库是MSSQL:
SELECT t.[taskId], tq.name as taskName,
CASE
WHEN (ROW_NUMBER() OVER(PARTITION BY tq.name ORDER BY tq.name))%3 = 0 THEN 3
ELSE (ROW_NUMBER() OVER(PARTITION BY tq.name ORDER BY tq.name))%3
END AS RowNum
FROM Task t (NOLOCK)
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