如何在SQL查询结果中将NULL值替换为0

Question

SELECT  EmployeeMaster.EmpNo, Sum(LeaveApplications.LeaveDaysTaken) AS LeaveDays
    FROM  EmployeeMaster  FULL OUTER JOIN
    LeaveApplications ON EmployeeMaster.id = LeaveApplications.EmployeeRecordID INNER JOIN
    LeaveMaster ON EmployeeMaster.id = LeaveMaster.EmpRecordID
    GRoup BY EmployeeMaster.EmpNo
    order by LeaveDays Desc

使用上述查询，如果员工在表 LeaveApplications 中没有离开应用程序记录，那么他们的 Sum（LeaveApplications.LeaveDaysTaken）AS LeaveDays 列将返回NULL。我想要做的是将值0（零）而不是NULL。我想这样做，因为我在同一查询中有一个计算列，其公式取决于返回的LeaveDays，当LeaveDays为NULL时，公式表示一些失败。有没有我可以把0为NULL，这样我就可以得到我想要的结果。

Answer 1

SELECT  EmployeeMaster.EmpNo, ISNULL(Sum(LeaveApplications.LeaveDaysTaken),0) AS LeaveDays
    FROM  EmployeeMaster  FULL OUTER JOIN
    LeaveApplications ON EmployeeMaster.id = LeaveApplications.EmployeeRecordID INNER JOIN
    LeaveMaster ON EmployeeMaster.id = LeaveMaster.EmpRecordID
    GRoup BY EmployeeMaster.EmpNo
    order by LeaveDays Desc

Answer 2

您可能想要使用ISNULL

ISNULL(SUM(LeaveApplications.LeaveDaysTaken), 0) AS LeaveDays

Answer 3

使用isnull功能。