SQL - 将 NULL 值更改为 0答案

【问题标题】：SQL - Change NULL value to 0SQL - 将 NULL 值更改为 0
【发布时间】：2015-08-16 00:10:32
【问题描述】：

我有一个在 SUM(contar) 上为我提供空值的数据透视表，我想将它们更改为 0

SELECT Description AS Categoria,
       [ACS],
       [URO]
FROM
  (SELECT GroupType.Description,
          Speciality.Shortname,
          SUM(1) AS contar
   FROM DoctorEnterpriseDetails
   INNER JOIN Speciality ON DoctorEnterpriseDetails.Speciality1 = Speciality.SpecialityId
   INNER JOIN GroupType ON DoctorEnterpriseDetails.GroupId = GroupType.GroupId
   WHERE (DoctorEnterpriseDetails.EnterpriseId = 48)
   GROUP BY GroupType.Description,
            Speciality.Shortname) AS ps PIVOT (SUM(contar)
                                               FOR Shortname IN ([ACS],[URO])) pvt
ORDER BY description

我尝试过这种方式，但它再次给了我 Null 值

SELECT Description AS Categoria,
       [ACS],
       [URO]
FROM
  (SELECT GroupType.Description,
          Speciality.Shortname,
          GroupType.GroupId,
          (CASE WHEN (SUM(1) IS NULL) THEN 0 ELSE SUM(1) END) AS contar
   FROM DoctorEnterpriseDetails
   INNER JOIN Speciality ON DoctorEnterpriseDetails.Speciality1 = Speciality.SpecialityId
   INNER JOIN GroupType ON DoctorEnterpriseDetails.GroupId = GroupType.GroupId
   WHERE (DoctorEnterpriseDetails.EnterpriseId = 48)
   GROUP BY GroupType.Description,
            Speciality.Shortname,
            DoctorEnterpriseDetails.GroupId,
            GroupType.GroupId) AS ps PIVOT (SUM(contar)
                                            FOR Shortname IN ([ACS],[URO])) pvt
ORDER BY GroupId;

我不明白出了什么问题。谢谢

【问题讨论】：

标签： sql null pivot

【解决方案1】：

您在 CASE 中定义别名，这是不允许的。此外，您可以混合使用数字和字符串：

要么是

CASE WHEN SUM(1) IS NULL THEN 0 ELSE SUM(1) END AS contador

或

COALESCE(SUM(1), 0) END AS contador

顺便说一句，SUM(1) 与 COUNT(*) 相同

【讨论】：