Sql server 将表达式转换为标量函数时使用CASE-WHEN-T-SQL

下面我有一个标量值函数，但我想在表达式中添加一个CASE，但到目前为止未能正确使用语法

USE [MYDatabaseName]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER FUNCTION [dbo].[leaveBalanceByEmployeeID] (@EmployeeID INT)
RETURNS decimal(10,1)
AS
BEGIN
  DECLARE @returnValue decimal(10,1)
 SELECT @returnValue = MIN(dbo.LeaveMaster.LeaveDaysCarriedFoward + dbo.MonthsInService(dbo.LeaveMaster.DaysCarriedFowardCutoffDate, GETDATE()) 
            * dbo.EmployeeTypes.MonthlyLeaveAssignment)  - (SELECT     ISNULL(SUM(ActualLeaveDaysTaken), 0) AS LV
           FROM  dbo.LeaveApplications
           WHERE (EmployeeRecordID = dbo.EmployeeMaster.id AND HRMApproval = 'True' AND MarkAsDeleted = 'False'))  - CASE WHEN 0 <
           (SELECT ISNULL(SUM(DaysAuthorised),0) AS ECL
           FROM  dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_2
           WHERE (MasterEmployeeID = dbo.EmployeeMaster.id AND YEAR(CompassionateLeaveApplications_2.AuthorisedFromDate) =YEAR(GETDate())))  - ISNULL(MAX(dbo.Districts.CompassionateDays),0) THEN
           (SELECT  ISNULL(SUM(DaysAuthorised),0) AS ECL
           FROM   dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_2
           WHERE  (MasterEmployeeID = dbo.EmployeeMaster.id) AND YEAR(CompassionateLeaveApplications_2.AuthorisedFromDate) =YEAR(GETDate())) - ISNULL(MAX(dbo.Districts.CompassionateDays),0) ELSE 0 END                                                     
FROM       dbo.EmployeeMaster Full outer join dbo.LeaveMaster ON dbo.EmployeeMaster.id = dbo.LeaveMaster.EmpRecordID Full outer join
                      dbo.EmployeeTypes ON dbo.EmployeeMaster.EmployeeType = dbo.EmployeeTypes.ID Full outer join
                      Human_Resources.Departments ON dbo.EmployeeMaster.DepartmentId = Human_Resources.Departments.DepartmentID Full outer join
                      dbo.StaffHomeAddresses ON dbo.EmployeeMaster.id = dbo.StaffHomeAddresses.StaffID Full outer join
                      dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_1 ON 
                      dbo.EmployeeMaster.id = CompassionateLeaveApplications_1.MasterEmployeeID Full outer join
                      dbo.Districts ON dbo.StaffHomeAddresses.District = dbo.Districts.DistrictID
                      WHERE    dbo.EmployeeMaster.id = @EmployeeID
GROUP BY dbo.EmployeeMaster.id
return @returnValue
END

现在表dbo.EmployeeMaster有一个名为IsActive的位列。我想要实现的是，如果IsActive column=True，那么@returnValue应该返回上面的查询将返回的内容，否则如果IsActive=False，那么我只想返回0.0，为什么不添加一个if-else构造并相应地进行查询，如下所示

USE [MYDatabaseName]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER FUNCTION [dbo].[leaveBalanceByEmployeeID] (@EmployeeID INT)
RETURNS decimal(10,1)
AS
BEGIN
  DECLARE @returnValue decimal(10,1),@isActive bit;
  SELECT @isActive = IsActive FROM dbo.EmployeeMaster WHERE id = @EmployeeID;
  IF @isActive = 1
  BEGIN
  SELECT @returnValue = MIN(dbo.LeaveMaster.LeaveDaysCarriedFoward + dbo.MonthsInService(dbo.LeaveMaster.DaysCarriedFowardCutoffDate, GETDATE()) 
            * dbo.EmployeeTypes.MonthlyLeaveAssignment)  - (SELECT     ISNULL(SUM(ActualLeaveDaysTaken), 0) AS LV
           FROM  dbo.LeaveApplications
           WHERE (EmployeeRecordID = dbo.EmployeeMaster.id AND HRMApproval = 'True' AND MarkAsDeleted = 'False'))  - CASE WHEN 0 <
           (SELECT ISNULL(SUM(DaysAuthorised),0) AS ECL
           FROM  dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_2
           WHERE (MasterEmployeeID = dbo.EmployeeMaster.id AND YEAR(CompassionateLeaveApplications_2.AuthorisedFromDate) =YEAR(GETDate())))  - ISNULL(MAX(dbo.Districts.CompassionateDays),0) THEN
           (SELECT  ISNULL(SUM(DaysAuthorised),0) AS ECL
           FROM   dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_2
           WHERE  (MasterEmployeeID = dbo.EmployeeMaster.id) AND YEAR(CompassionateLeaveApplications_2.AuthorisedFromDate) =YEAR(GETDate())) - ISNULL(MAX(dbo.Districts.CompassionateDays),0) ELSE 0 END                                                     
  FROM       dbo.EmployeeMaster Full outer join dbo.LeaveMaster ON dbo.EmployeeMaster.id = dbo.LeaveMaster.EmpRecordID Full outer join
                      dbo.EmployeeTypes ON dbo.EmployeeMaster.EmployeeType = dbo.EmployeeTypes.ID Full outer join
                      Human_Resources.Departments ON dbo.EmployeeMaster.DepartmentId = Human_Resources.Departments.DepartmentID Full outer join
                      dbo.StaffHomeAddresses ON dbo.EmployeeMaster.id = dbo.StaffHomeAddresses.StaffID Full outer join
                      dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_1 ON 
                      dbo.EmployeeMaster.id = CompassionateLeaveApplications_1.MasterEmployeeID Full outer join
                      dbo.Districts ON dbo.StaffHomeAddresses.District = dbo.Districts.DistrictID
                      WHERE    dbo.EmployeeMaster.id = @EmployeeID
GROUP BY dbo.EmployeeMaster.id
END
ELSE 
BEGIN
SET @returnValue = 0;
END
return @returnValue
END

---

如果未激活，只需使用所需值初始化变量：

DECLARE @returnValue decimal(10,1) = 0.0

修改Where calusule以检查是否处于活动状态

 WHERE    dbo.EmployeeMaster.id = @EmployeeID and dbo.EmployeeMaster.IsActive = 1

通过添加该条件，变量将仅在激活时更新，在另一种情况下，它将包含您在初始化中使用的值

USE [MYDatabaseName]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER FUNCTION [dbo].[leaveBalanceByEmployeeID] (@EmployeeID INT)
RETURNS decimal(10,1)
AS
BEGIN
  DECLARE @returnValue decimal(10,1) = 0.0
 SELECT @returnValue = MIN(dbo.LeaveMaster.LeaveDaysCarriedFoward + dbo.MonthsInService(dbo.LeaveMaster.DaysCarriedFowardCutoffDate, GETDATE()) 
            * dbo.EmployeeTypes.MonthlyLeaveAssignment)  - (SELECT     ISNULL(SUM(ActualLeaveDaysTaken), 0) AS LV
           FROM  dbo.LeaveApplications
           WHERE (EmployeeRecordID = dbo.EmployeeMaster.id AND HRMApproval = 'True' AND MarkAsDeleted = 'False'))  - CASE WHEN 0 <
           (SELECT ISNULL(SUM(DaysAuthorised),0) AS ECL
           FROM  dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_2
           WHERE (MasterEmployeeID = dbo.EmployeeMaster.id AND YEAR(CompassionateLeaveApplications_2.AuthorisedFromDate) =YEAR(GETDate())))  - ISNULL(MAX(dbo.Districts.CompassionateDays),0) THEN
           (SELECT  ISNULL(SUM(DaysAuthorised),0) AS ECL
           FROM   dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_2
           WHERE  (MasterEmployeeID = dbo.EmployeeMaster.id) AND YEAR(CompassionateLeaveApplications_2.AuthorisedFromDate) =YEAR(GETDate())) - ISNULL(MAX(dbo.Districts.CompassionateDays),0) ELSE 0 END                                                     
FROM       dbo.EmployeeMaster Full outer join dbo.LeaveMaster ON dbo.EmployeeMaster.id = dbo.LeaveMaster.EmpRecordID Full outer join
                      dbo.EmployeeTypes ON dbo.EmployeeMaster.EmployeeType = dbo.EmployeeTypes.ID Full outer join
                      Human_Resources.Departments ON dbo.EmployeeMaster.DepartmentId = Human_Resources.Departments.DepartmentID Full outer join
                      dbo.StaffHomeAddresses ON dbo.EmployeeMaster.id = dbo.StaffHomeAddresses.StaffID Full outer join
                      dbo.CompassionateLeaveApplications AS CompassionateLeaveApplications_1 ON 
                      dbo.EmployeeMaster.id = CompassionateLeaveApplications_1.MasterEmployeeID Full outer join
                      dbo.Districts ON dbo.StaffHomeAddresses.District = dbo.Districts.DistrictID
                      WHERE    dbo.EmployeeMaster.id = @EmployeeID and dbo.EmployeeMaster.IsActive = 1 
GROUP BY dbo.EmployeeMaster.id
return @returnValue
END

---

这就是为什么我声明了一个变量，并用给定员工ID的IsActive列的值填充它。该变量用于计算该值