在 MS-SQL 中将行数据分组并求和到列中？

原始问题

我不知道我是否应该提出一个新问题或取消标记最后一个问题！ 所以，我想做的是：

WorkWeek  Catg  Item    Cost
WorkWeek1 Cat1  Item1   Price
WorkWeek1 Cat1  Item2   Price
WorkWeek1 Cat2  Item3   Price
WorkWeek1 Cat3  Item4   Price
WorkWeek1 Cat3  Item1   Price
WorkWeek2 Cat1  Item1   Price
WorkWeek2 Cat2  Item2   Price
WorkWeek3 Cat1  Item1   Price
WorkWeek4 Cat1  Item2   Price
.
.
WorkWeekA CatB  ItemC   Price

我想创建一个新表，列出每个工作周，然后列出该工作周中每个类别的价格总计。这就是我现在正在做的事情，但是查询只是将每个 ww 的所有内容相加，为所有工作周提供相同的总和：

select
    workweek
    ,(select sum(cost) from DataTable where Catg = 'Cat1') as Cat1TotalCost
    ,(select sum(cost) from DataTable where Catg = 'Cat2') as Cat2TotalCost
    ,(select sum(cost) from DataTable where Catg = 'Cat3') as Cat3TotalCost
    .
    .
    .
    .
from DataTable
group by Workweek

您还可以像这样进行枢轴操作：

select workweek,
       sum(case when Catg = 'Cat1' then cost end) as Cat1TotalCost,
       sum(case when Catg = 'Cat2' then cost end) as Cat2TotalCost,
       sum(case when Catg = 'Cat3' then cost end) as Cat3TotalCost
from DataTable
group by Workweek

您不应该为每个值执行单独的子查询。

The pivot声明也是一个非常合理的选择。我倾向于坚持使用显式版本（上面），因为它让我在添加列时更加灵活。