sql-server - 如何在 Sql 中创建 "month"列？

Question

我有一组数据，看起来像这样(非常简化):

productId    Qty   dateOrdered
---------    ---   -----------
       1       2    10/10/2008
       1       1    11/10/2008
       1       2    10/10/2009
       2       3    10/12/2009
       1       1    10/15/2009
       2       2    11/15/2009

除此之外，我们尝试创建一个查询来获取如下内容:

productId  Year  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
---------  ----  --- --- --- --- --- --- --- --- --- --- --- ---
        1  2008    0   0   0   0   0   0   0   0   0   2   1   0
        1  2009    0   0   0   0   0   0   0   0   0   3   0   0
        2  2009    0   0   0   0   0   0   0   0   0   3   2   0

我现在这样做的方式是，我正在执行 12 个选择，每个月一个，并将它们放入临时表中。然后我做了一个巨大的加入。一切正常，但这家伙太慢了。

Answer 1

select productId, Year(dateOrdered) Year
  ,isnull(sum(case when month(dateOrdered) = 1 then Qty end), 0) Jan
  ,isnull(sum(case when month(dateOrdered) = 2 then Qty end), 0) Feb 
  ,isnull(sum(case when month(dateOrdered) = 3 then Qty end), 0) Mar
  ,isnull(sum(case when month(dateOrdered) = 4 then Qty end), 0) Apr
  ,isnull(sum(case when month(dateOrdered) = 5 then Qty end), 0) May
  ,isnull(sum(case when month(dateOrdered) = 6 then Qty end), 0) Jun
  ,isnull(sum(case when month(dateOrdered) = 7 then Qty end), 0) Jul
  ,isnull(sum(case when month(dateOrdered) = 8 then Qty end), 0) Aug
  ,isnull(sum(case when month(dateOrdered) = 9 then Qty end), 0) Sep
  ,isnull(sum(case when month(dateOrdered) = 10 then Qty end), 0) Oct
  ,isnull(sum(case when month(dateOrdered) = 11 then Qty end), 0) Nov
  ,isnull(sum(case when month(dateOrdered) = 12 then Qty end), 0) Dec
from Table1
group by productId, Year(dateOrdered)

SQL Fiddle