SQL server View - 循环帮助（while循环）

Question

我被要求使用SQL中的视图生成数据集，并且有许多产品（例如＆＃39; a＆＃39;＆＃39; b＆＃39;，＆＃39 ; c c＆＃39;）我希望计算总数超过5年（1,2,3,4,5）并输出总数为total_a_a_yr1，total_b_b_yr1 ....（见下面的代码）

有没有更有效的编码方式，而不是写出大量的代码行？

我考虑过创建一个程序，但我认为你不能在视图中使用EXEC。我可能错了。一个while循环可能是要走的路，但我不确定在视图中使用声明。

任何帮助将不胜感激。感谢

,sum(case when product = 'a a' and floor(datediff(dd, date1,date2)/365.25)<1  
                        then amount_received else null end) as total_a_a_yr1

,sum(case when product = 'a a' and floor(datediff(dd, date1,date2)/365.25)<(2) 
                        then amount_received else null end) as total_a_a_yr2

,sum(case when product = 'a a' and floor(datediff(dd, date1,date2)/365.25)<(3)
                        then amount_received else null end) as total_a_a_yr3

,sum(case when product = 'a a' and floor(datediff(dd, date1,date2)/365.25)<(4) 
                        then amount_received else null end) as total_a_a_yr4    

,sum(case when product = 'a a' and floor(datediff(dd, date1,date2/365.25)<(5) 
                        then amount_received else null end) as total_a_a_yr5

Answer 1

首先，case语句的默认值为NULL，因此＆＃34; ELSE NULL＆＃34;没有必要。其次，这个公式可能不完全符合您的想法：floor(datediff(dd, date1,date2)/365.25)。我的意思是，如果您假设每四年有一个闰年，那么您就错了。闰年不会在被100整除的年份发生，除非它也可以除以400.但我可能误解了你想要做的事情。

您是正确的，您无法在视图中使用动态SQL（例如EXEC '<sql code>'）。 对tally table的影响很小。以下是使用计数表以编程方式生成代码的方式（我将使用1到100）：

with yourExpression(ex) as
(
  select ',sum(case when product = ''''a a'''' and floor(datediff(dd, date1,date2)/365.25)<
                        then amount_received else null end) as total_a_a_yr'
),
iTally(N) as
(
  select top(100) cast(row_number() over (order by (select null)) as varchar(3))
  from sys.all_columns
)
select stuff(ex,78,0,'('+N+')')+N
from iTally
cross join yourExpression;

您可以按原样复制/粘贴并执行查询;它将返回：

,sum(case when product = ''a a'' and floor(datediff(dd, date1,date2)/365.25)<(1)
                            then amount_received else null end) as total_a_a_yr1
,sum(case when product = ''a a'' and floor(datediff(dd, date1,date2)/365.25)<(2)
                            then amount_received else null end) as total_a_a_yr2
,sum(case when product = ''a a'' and floor(datediff(dd, date1,date2)/365.25)<(3)....
--<truncated for brevity> ... as total_a_a_yr100