使用 Case When 时的不同计数

Question

在 SQL 服务器中使用 case when 和 distinct 时，我无法获得正确的非重复计数。

我有一列 count(distinct TA_STUDENT_ID) 可以计算出正确的计数。然后我有 2 个额外的列，我在其中按 TA_LOCATION 进行计数，TA_LOCATION 下每一行的数字总计需要加起来等于 DISTINCT TA_STUDENT_ID 的计数。我需要帮助才能做到这一点。这是我的查询：

SELECT 
count  (distinct TA_STUDENT_ID) as 'count',
COUNT (CASE WHEN (TA_LOCATION = 'CCC') THEN 'CCC'  END) AS 'CCC',
COUNT(CASE WHEN (TA_LOCATION = 'SCCDC') THEN 'SCCDC'  END) AS 'SCCDC',      
[TA_AW_ID]
FROM  [S85_TA_ACYR]
group by   [TA_AW_ID]
order by  [TA_AW_ID]

我想要的结果是 TA_LOCATION 列中每一行的总数应该总计并与我的 COUNT DISTINCT TA_STUDENT_ID 列中的行数相匹配。

Answer 1

在 COUNT() 中使用 DISTINCT 和 CASE 表达式：

SELECT COUNT(DISTINCT TA_STUDENT_ID) as 'count',
       COUNT(DISTINCT CASE WHEN (TA_LOCATION = 'CCC') THEN TA_STUDENT_ID  END) AS 'CCC',
       COUNT(DISTINCT CASE WHEN (TA_LOCATION = 'SCCDC') THEN TA_STUDENT_ID  END) AS 'SCCDC',      
       [TA_AW_ID]
FROM  [S85_TA_ACYR]
GROUP BY [TA_AW_ID]
ORDER BY [TA_AW_ID];

Answer 2

您还可以对后两个字段使用 SUM()，如下所示：

SELECT
    Count = COUNT(DISTINCT TA_STUDENT_ID)
    ,CCC = SUM(CASE WHEN ( TA_LOCATION = 'CCC' ) THEN 1 ELSE 0 END)
    ,SCCDC = SUM(CASE WHEN ( TA_LOCATION = 'SCCDC' ) THEN 1 ELSE 0 END)
    ,TA_AW_ID
FROM S85_TA_ACYR
GROUP BY TA_AW_ID
ORDER BY TA_AW_ID

使用 Case When 时的不同计数

Distinct Count when using Case When

sql-server

distinct

case-when