[英]SQL Server 2012: Conditionally Incrementing a counter user ROW_NUMBER()
I am trying to apply ROW_NUMBER()
to increment a counter based on particular conditions. 我正在尝试应用ROW_NUMBER()
来根据特定条件递增计数器。
My data looks like this, with the target counter being the Prep
column 我的数据看起来像这样,目标计数器是Prep
列
id DSR PrepIndicator Prep
--------------------------------------
1662835 -1 1 1
1662835 14 2 2
1662835 14 2 3
1662835 20 2 4
1667321 -1 1 1
1667321 30 2 2
1667321 14 2 3
1680648 -1 1 1
1680648 14 2 2
1680648 60 1 1
1680648 14 2 2
1680648 14 2 3
1683870 -1 1 1
1683870 12 2 2
1683870 10 2 3
1683870 60 1 1
1683870 7 2 2
Ignoring the PrepIndicator
column for the moment, the business logic I am trying to implement is as follows: PrepIndicator
忽略PrepIndicator
列,我试图实现的业务逻辑如下:
Prep
counter if the DSR is less than 42. 对于每个Id,从1开始,如果DSR小于42,则递增Prep
计数器。 The PrepIndicator
, in effect, creates a flag to implement this, in that if PrepIndicator = 1
then Prep = 1
. 实际上, PrepIndicator
会创建一个标志来实现它,如果PrepIndicator = 1
则Prep = 1
。 If PrepIndicator = 2
, then increment Prep
. 如果PrepIndicator = 2
,则增加Prep
。
I'd prefer to achieve this without the PrepIndicator
column if possible. 如果可能的话,我更愿意在没有PrepIndicator
专栏的情况下实现这一PrepIndicator
。
How would I achieve this conditional increment with ROW_NUMBER()
? 如何使用ROW_NUMBER()
实现此条件增量?
I've tried 我试过了
ROW_NUMBER() OVER (PARTITION BY id, PrepIndicator ORDER BY id)
but it doesn't seem to work when the DSR
is >= 42
. 但是当DSR
>= 42
时它似乎不起作用。
Any suggestions or help would be great. 任何建议或帮助都会很棒。 Thanks! 谢谢!
First, you will need explicit ordering. 首先,您需要明确的订购。 "Incrementing the counter" only has meaning if you have a previous value. 如果你有一个以前的值,“递增计数器”只有意义。 You can add an IDENTITY column to the table, or use ROW_NUMBER() OVER ORDER BY(/* your logic here */)
. 您可以向表中添加IDENTITY列,或使用ROW_NUMBER() OVER ORDER BY(/* your logic here */)
。 In your table, you do not even have unique values for the first three columns (see 1680648, 14, 2), so I would think adding an ID is the way to go. 在您的表中,您甚至没有前三列的唯一值(请参阅1680648,14,2),因此我认为添加ID是可行的方法。
To do what you want to achieve, I believe you must do this in a loop. 为了做你想要达到的目标,我相信你必须在循环中做到这一点。 If you use ROW_NUMBER()
you may wish to select into a temporary table. 如果您使用ROW_NUMBER()
您可能希望选择一个临时表。 By the nature of your question, the term counter indicates you will have a variable. 根据您的问题的性质,术语计数器表示您将拥有一个变量。
UPDATE TableA SET rowId = ROW_NUMBER() OVER(ORDER BY id, DSR, PrepIndicator)
then "conditional" seems to signal a good use of CASE 然后“有条件的”似乎表明了CASE的良好用途
DECLARE @counter INT = 1
DECLARE @row INT = 1
DECLARE @DSR INT
UPDATE TableA SET Prep = @counter
SET @row = (SELECT rowId FROM TableA WHERE rowId > @row)
WHILE EXISTS( SELECT TOP 1 1 FROM TableA WHERE rowId = @row )
BEGIN
SELECT @DSR = DSR FROM TableA WHERE rowId = @row
SET @counter = CASE WHEN @DSR < 42 THEN @counter + 1 ELSE 1 END
UPDATE TableA SET Prep = @counter WHERE rowId = @row
SET @row = (SELECT rowId FROM TableA WHERE rowId > @row)
END
First, you need to add a primary key because there is no physical order in a SQL table; 首先,您需要添加主键,因为SQL表中没有物理顺序; we can call it IdK. 我们可以称之为IdK。 The following code should then give you what you want: 然后,以下代码应该为您提供所需内容:
select *, row_number() over (partition by Id, (Select Count (*) from MyTable t2 where t2.idk <= t1.idk and t2.id = t1.id and DSR >= 42) order by idk) prep
from MyTable t1
order by idk
As to why your code doesn't work, this is because the rows are first grouped before the partition/numbering is done. 至于为什么你的代码不起作用,这是因为在分区/编号完成之前首先对行进行分组。 In the case with the two columns id and PrepIndicator for the partition, we get the following intermediary result for the last 5 row before the numbering: 在分区的两列id和PrepIndicator的情况下,我们在编号之前的最后5行获得以下中间结果:
id DSR PrepIndicator Row_Number (Id, PrepIndicator)
1683870 -1 1 1
1683870 60 1 2
1683870 12 2 1
1683870 10 2 2
1683870 7 2 3
Notice that the line with DSR = 60 is now in the second position. 请注意,DSR = 60的行现在位于第二个位置。 This is clearly what you don't want to have. 这显然是你不想拥有的。 In the case with the Select count(*)..., we have the following result for the last 5 rows after the grouping is done, just before the numbering: 在Select count(*)...的情况下,我们在分组完成后的最后5行中得到以下结果,就在编号之前:
id DSR ...Count() Row_Number (Id, ...Count())
1683870 -1 0 1
1683870 12 0 2
1683870 10 0 3
1683870 60 1 1
1683870 7 1 2
You can notice that in this case, there is no change of position for any row. 您可以注意到,在这种情况下,任何行的位置都没有变化。
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