如何用sql server中的group by和where显示数据？

Question

我用这个案例来显示数据跟随where和group by。以下是18/12/2017的样本。

SELECT 
    PROID,
    MAX(COUNT_NUMBER) AS COUNT_NUMBER_OLD,
    CONVERT(CHAR(10), DATETIME_INPUT, 101) AS PreDate
FROM 
    TABLE_A
WHERE 
    CONVERT(VARCHAR(2), DATETIME_INPUT, 108) BETWEEN '18' AND '23'
    AND CONVERT(CHAR(10), DATETIME_INPUT, 103) = '18/12/2017'
GROUP BY 
    PROID, CONVERT(CHAR(10), DATETIME_INPUT, 101);

结果是：

PROID     COUNT_NUMBER_OLD      PreDate
-------------------------------------------
01        1063                  12/18/2017
02        365                   12/18/2017
03        845                   12/18/2017

它工作正常，但我想显示数据，如果没有数据在where条件。例如：CONVERT(CHAR(10), DATETIME_INPUT, 103) = '17/12/2017'：

PROID     COUNT_NUMBER_OLD      PreDate
------------------------------------------
01        0                     12/17/2017
02        0                     12/17/2017
03        0                     12/17/2017

我试着用

(CASE 
    WHEN COUNT_NUMBER IS NULL 
       THEN 0 
       ELSE MAX(COUNT_NUMBER) 
 END) AS COUNT_NUMBER_OLD

但我得到这个错误：

“TABLE_A.COUNT_NUMBER”列在选择列表中无效，因为它不包含在聚合函数或GROUP BY子句中。

Answer 1

您可以使用子查询并获取每个组的max count_number，然后执行ISNULL操作。

SELECT X.PROID,
       ISNULL(X.COUNT_NUMBER,0) AS COUNT_NUMBER_OLD,
       X.PreDate
FROM
(SELECT PROID,
       ROW_NUMBER() OVER (PARTITION BY PROID,CONVERT(CHAR(10), DATETIME_INPUT, 101) ORDER BY COUNT_NUMBER DESC) AS RN,
       CONVERT(CHAR(10), DATETIME_INPUT, 101) AS PreDate,
       COUNT_NUMBER
FROM TABLE_A
WHERE CONVERT(VARCHAR(2), DATETIME_INPUT, 108) BETWEEN '18' AND '23'
      AND CONVERT(CHAR(10), DATETIME_INPUT, 103) = '18/12/2017' ) X
WHERE X.RN=1

Answer 2

我觉得你的列可能有NULL值。

默认情况下，MAX和MIN函数在评估数据时不计算NULL。如果COUNT_NUMBER列包含NULL值，则MAX和MIN都将忽略该值。

试试这个解决方案

SELECT PROID,
       MAX(COALESCE(COUNT_NUMBER,0)) AS COUNT_NUMBER_OLD,
       CONVERT(CHAR(10), DATETIME_INPUT, 101) AS PreDate
FROM TABLE_A
WHERE CONVERT(VARCHAR(2), DATETIME_INPUT, 108) BETWEEN '18' AND '23'
AND CONVERT(CHAR(10), DATETIME_INPUT, 103) = '17/12/2017'
GROUP BY PROID,
         CONVERT(CHAR(10), DATETIME_INPUT, 101);