SQL Server枢轴使用案例语句 [英] SQL Server pivot using case statement

问题描述

我正在尝试提取一些数据，我想我需要在我的透视代码中合并一个case语句，但是我不确定该如何做.我有下表:

I'm trying to pivot out some data and I think I need to incorporate a case statement in my pivot code but I'm not sure how. I have the table below:

ID      AreaCode
1001    1501
1001    1502
1001    2301
1031    1010
1031    3012
1048    2304
1048    3012
1048    4022

每个AreaCode的第一位数字代表一个身体区域，我使用下面的代码表示受影响的身体区域:

The first digit of each AreaCode refers to a body area, I'm using the code below to indicate which body area is affected:

select id,
case when left(areaID,1)=1 then 'Yes' end Head,
case when left(areaID,1)=2 then 'Yes' end Face,
case when left(areaID,1)=3 then 'Yes' end Neck,
case when left(areaID,1)=4 then 'Yes' end Abdo
from #testcase

哪些给了我以下内容:

id      Head    Face    Neck    Abdo
1001    Yes     NULL    NULL    NULL
1001    Yes     NULL    NULL    NULL
1001    NULL    Yes     NULL    NULL
1031    Yes     NULL    NULL    NULL
1031    NULL    NULL    Yes     NULL
1048    NULL    Yes     NULL    NULL
1048    NULL    NULL    Yes     NULL
1048    NULL    NULL    NULL    Yes

但是，我需要我的输出表为每个id包含一行，就像这样:

However, I need my output table to contain one row for each id, like so:

id      Head    Face    Neck    Abdo
1001    Yes     Yes     Null    Null
1031    Yes     Null    Yes     Null
1048    Null    Yes     Yes     Yes

能否将我的case语句合并到一个枢轴中以实现此目的?谢谢

Can incorporate my case statement in a pivot to achieve this? Thanks

推荐答案

您需要在case语句的顶部使用aggregate

You need to use aggregate on top of case statements

SELECT id,
       Max(CASE
             WHEN LEFT(areaID, 1) = 1 THEN 'Yes'
           END) Head,
       Max(CASE
             WHEN LEFT(areaID, 1) = 2 THEN 'Yes'
           END) Face,
       Max(CASE
             WHEN LEFT(areaID, 1) = 3 THEN 'Yes'
           END) Neck,
       Max(CASE
             WHEN LEFT(areaID, 1) = 4 THEN 'Yes'
           END) Abdo
FROM   #testcase
GROUP  BY id 

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