ISNULL(Count(x),0)当为null时不返回0

Question

我有以下代码：

SELECT     FirstName, LastName,
(SELECT ISNULL(COUNT(UP1.EmailAddress), 0) AS HasEmail 
     From dbo.UserProfiles AS UP1 
     WHERE (NOT (UP1.EmailAddress IS NULL)) AND (CreatedBy = dbo.UserProfiles.UserID)
     GROUP BY CreatedBy) AS EmailEnteredCount FROM dbo.UserProfiles WHERE (IsStaff = 1)

示例结果：

LastName EmailEnteredCount

帐单为空

拉尔森51

克里斯蒂30

parrish NULL

senac NULL

代码可以正确执行，但有一个例外，当找不到任何记录时，它会返回一个空值，而不是预期的0。我也尝试过使用coalesce，但无济于事。

更新:这返回了我想要实现的东西，只需要一个更干净的解决方案。我真的不认为我需要创建一个临时表来替换空值。

drop table #tt
                    select userid,firstname, lastname, 
                    (
                      SELECT     count(*) AS HasEmail
                      FROM         dbo.UserProfiles AS UP1
                      WHERE     (UP1.EmailAddress IS NOT NULL)AND (UP1.CreatedBy = UserProfiles.UserId) and (datecreated between @startdate and @enddate)
                      GROUP BY CreatedBy
                    ) as EmailCount
                    into #tt
                    from dbo.UserProfiles where isstaff = 1

                    select userid,firstname, lastname, ISNULL(EmailCount,0) As EmailCount from #tt

任何帮助都将不胜感激。

谢谢，克里斯

Answer 1

您需要将isnull函数移到相关子查询之外，如下所示：

SELECT  FirstName, 
        LastName,
        IsNull((
            SELECT  COUNT(UP1.EmailAddress) AS HasEmail 
            From    dbo.UserProfiles AS UP1 
            WHERE   (NOT (UP1.EmailAddress IS NULL)) 
                    AND (CreatedBy = dbo.UserProfiles.UserID)
            GROUP BY CreatedBy), 0) AS EmailEnteredCount 
FROM    dbo.UserProfiles 
WHERE   (IsStaff = 1)

Answer 2

如果您的isnull在您的计数范围内，这会更有意义。试试这个：

count(isnull(up1.emailaddress, 0))