SQL sum by year report，寻找优雅的解决方案

SQL sum by year report, looking for an elegant solution(SQL sum by year report，寻找优雅的解决方案)

问题描述

我有一个包含 3 列的表:ItemCode、Quantity 和 DocDate.我想以更优雅"的方式创建以下报告:

I have a table with 3 columns: ItemCode, Quantity and DocDate. I would like to create the following report in a more "elegant" way:

SELECT T0.ItemCode, 
       (SELECT SUM(QUANTITY) FROM MyTable T1 WHERE YEAR(T0.DocDate) = 2011 AND T0.ItemCode = T1.ItemCode) AS '2011',
       (SELECT SUM(QUANTITY) FROM MyTable T1 WHERE YEAR(T0.DocDate) = 2012 AND T0.ItemCode = T1.ItemCode) AS '2012'
FROM MyTable T0
GROUP BY T0.ItemCode, YEAR(T0.DocDate)

我很确定有更好、更有效的方法来编写它，但我想不出正确的语法.有什么想法吗?

I'm pretty sure there's a better, more efficient way to write this but I can't come up with the right syntax. Any ideas?

推荐答案

你可以试试这个:

SELECT  T0.ItemCode, 
        SUM(CASE WHEN YEAR(T0.DocDate) = 2011 THEN QUANTITY ELSE 0 END) AS '2011',
        SUM(CASE WHEN YEAR(T0.DocDate) = 2012 THEN QUANTITY ELSE 0 END) AS '2012'
FROM    MyTable T0
GROUP BY 
        T0.ItemCode

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