使用 RANK() OVER 计数时跳过空值

Question

给定一组行，有时有字段null，有时没有：

SELECT 
   Date, TheThing
FROM MyData
ORDER BY Date


Date                     TheThing
-----------------------  --------
2016-03-09 08:17:29.867  a
2016-03-09 08:18:33.327  a
2016-03-09 14:32:01.240  NULL
2016-10-21 19:53:49.983  NULL
2016-11-12 03:25:21.753  b
2016-11-24 07:43:24.483  NULL
2016-11-28 16:06:23.090  b
2016-11-28 16:09:07.200  c
2016-12-10 11:21:55.807  c

我想要一个计算非空值的排名列：

Date                     TheThing  DesiredTotal
-----------------------  --------  ------------
2016-03-09 08:17:29.867  a         1
2016-03-09 08:18:33.327  a         2
2016-03-09 14:32:01.240  NULL      2 <---notice it's still 2 (good)
2016-10-21 19:53:49.983  NULL      2 <---notice it's still 2 (good)
2016-11-12 03:25:21.753  b         3
2016-11-24 07:43:24.483  NULL      3 <---notice it's still 3 (good)
2016-11-28 16:06:23.090  b         4
2016-11-28 16:09:07.200  c         5
2016-12-10 11:21:55.807  c         6

我尝试显而易见的方法：

SELECT 
   Date, TheThing, 
   RANK() OVER(ORDER BY Date) AS Total
FROM MyData
ORDER BY Date

但RANK()计算空值：

Date                     TheThing  Total
-----------------------  --------  -----
2016-03-09 08:17:29.867  a         1
2016-03-09 08:18:33.327  a         2
2016-03-09 14:32:01.240  NULL      3 <--- notice it is 3 (bad)
2016-10-21 19:53:49.983  NULL      4 <--- notice it is 4 (bad)
2016-11-12 03:25:21.753  b         5 <--- and all the rest are wrong (bad)
2016-11-24 07:43:24.483  NULL      7
2016-11-28 16:06:23.090  b         8
2016-11-28 16:09:07.200  c         9
2016-12-10 11:21:55.807  c         10

我如何指示RANK()（或DENSE_RANK()）不计算空值？

您尝试过使用分区吗？

为什么是！更糟糕：

SELECT 
   Date, TheThing, 
   RANK() OVER(PARTITION BY(CASE WHEN TheThing IS NOT NULL THEN 1 ELSE 0 END) ORDER BY Date) AS Total
FROM MyData
ORDER BY Date

但RANK()计算空值：

Date                     TheThing  Total
-----------------------  --------  -----
2016-03-09 08:17:29.867  a         1
2016-03-09 08:18:33.327  a         2
2016-03-09 14:32:01.240  NULL      1 <--- reset to 1?
2016-10-21 19:53:49.983  NULL      2 <--- why go up?
2016-11-12 03:25:21.753  b         3 
2016-11-24 07:43:24.483  NULL      3 <--- didn't reset?
2016-11-28 16:06:23.090  b         4 
2016-11-28 16:09:07.200  c         5
2016-12-10 11:21:55.807  c         6

现在我随机输入一些东西——疯狂地挥舞。

SELECT 
   Date, TheThing, 
   RANK() OVER(PARTITION BY(CASE WHEN TheThing IS NOT NULL THEN 1 ELSE NULL END) ORDER BY Date) AS Total
FROM MyData
ORDER BY Date

SELECT 
   Date, TheThing, 
   DENSE_RANK() OVER(PARTITION BY(CASE WHEN TheThing IS NOT NULL THEN 1 ELSE NULL END) ORDER BY Date) AS Total
FROM MyData
ORDER BY Date

编辑：有了所有答案，需要多次迭代才能找到我不想要的所有边缘情况。最后我在概念上想要的是OVER()为了计数。我不知道OVER可以应用于RANK( 和DENSE_RANK) 以外的任何东西。

http://sqlfiddle.com/#!18/c6d87/1

奖励阅读

• 如何在 SQL Server 中使用 RANK()
• 不计算空值的 RANK
• SQL Server 2012 PERCENT_RANK() 排除 NULL
• 使用 DENSE_RANK 排除空值

Answer 1

我认为您正在寻找累积计数：

SELECT Date, TheThing, 
       COUNT(theThing) OVER (ORDER BY Date) AS Total
FROM MyData
ORDER BY Date;