如何按以下别名列分组答案

【问题标题】：How to group by the following aliased column如何按以下别名列分组
【发布时间】：2017-05-12 12:49:49
【问题描述】：

您将如何在以下查询中按别名列 Test_Quarter 进行分组：

SELECT  a.testID, 
        a.projectYear ,
        CASE a.ProjectPeriod
            WHEN 1 THEN 1
            WHEN 2 THEN 1
            WHEN 3 THEN 1
            WHEN 4 THEN 2
            WHEN 5 THEN 2
            WHEN 6 THEN 2
            WHEN 7 THEN 3
            WHEN 8 THEN 3
            WHEN 9 THEN 3
            WHEN 10 THEN 4
            WHEN 11 THEN 4
            WHEN 12 THEN 4 
        END AS Test_Quarter,
        SUM(a.cost)
FROM    test a
GROUP   BY a.testID, a.projectYear, Test_Quarter

谢谢你，

【问题讨论】：

你可以和a.Test_Quarter一样使用或者放置所有case语句

标签： sql sql-server database group-by

【解决方案1】：

在按子句分组中包含案例陈述

SELECT  a.testID, 
        a.projectYear ,
        CASE a.ProjectPeriod
            WHEN 1 THEN 1
            WHEN 2 THEN 1
            WHEN 3 THEN 1
            WHEN 4 THEN 2
            WHEN 5 THEN 2
            WHEN 6 THEN 2
            WHEN 7 THEN 3
            WHEN 8 THEN 3
            WHEN 9 THEN 3
            WHEN 10 THEN 4
            WHEN 11 THEN 4
            WHEN 12 THEN 4 
        END AS Test_Quarter,
        SUM(a.cost)
FROM    test a
GROUP   BY a.testID, a.projectYear, CASE a.ProjectPeriod
            WHEN 1 THEN 1
            WHEN 2 THEN 1
            WHEN 3 THEN 1
            WHEN 4 THEN 2
            WHEN 5 THEN 2
            WHEN 6 THEN 2
            WHEN 7 THEN 3
            WHEN 8 THEN 3
            WHEN 9 THEN 3
            WHEN 10 THEN 4
            WHEN 11 THEN 4
            WHEN 12 THEN 4 
        END

【讨论】：

【解决方案2】：

SELECT  a.testID, 
        a.projectYear ,
        CASE a.ProjectPeriod
            WHEN 1 THEN 1
            WHEN 2 THEN 1
            WHEN 3 THEN 1
            WHEN 4 THEN 2
            WHEN 5 THEN 2
            WHEN 6 THEN 2
            WHEN 7 THEN 3
            WHEN 8 THEN 3
            WHEN 9 THEN 3
            WHEN 10 THEN 4
            WHEN 11 THEN 4
            WHEN 12 THEN 4 
        END AS Test_Quarter,
        SUM(a.cost)
FROM    test a
GROUP   BY a.testID, a.projectYear,CASE a.ProjectPeriod
            WHEN 1 THEN 1
            WHEN 2 THEN 1
            WHEN 3 THEN 1
            WHEN 4 THEN 2
            WHEN 5 THEN 2
            WHEN 6 THEN 2
            WHEN 7 THEN 3
            WHEN 8 THEN 3
            WHEN 9 THEN 3
            WHEN 10 THEN 4
            WHEN 11 THEN 4
            WHEN 12 THEN 4 
        END

【讨论】：