how to replace empty values to zero in storedprocedure

USE [ACube_PRL]

GO

/****** Object: StoredProcedure [PAY].[usp_YTDSum] Script Date: 3/9/2016 3:38:24 PM ******/

SET ANSI_NULLS ON

GO

SET QUOTED_IDENTIFIER ON

GO

ALTER

PROCEDURE [PAY].[usp_YTDSum]

@EmpId int

AS

BEGIN

BEGIN TRY

SELECT * FROM (

select PC.EmpId, PC.SalaryComponentId, SC.Description,PC.Amount,CG.GroupName,

Convert(varchar(20),left(DATENAME(MONTH,PC.CreatedDateTime),3))+'_'+CONVERT(varchar,DATENAME(YEAR,PC.CreatedDateTime)) as MonthYear

from PAY.PaySlipComponents PC

INNER JOIN PAY.SalaryComponents SC ON PC.SalaryComponentId = SC.SalaryComponentId

INNER JOIN PAY.ComponentGroups CG ON SC.GroupId = CG.GroupId

WHERE PC.EmpId = @EmpId AND SC.Description <> 'MonthlyCTC'

) as s

UNION

SELECT * FROM(

select OSD.EmpId, OSD.SalaryComponentId, SC.Description,OSD.Amount,CG.GroupName,

Convert(varchar(20),left(DATENAME(MONTH,OSD.CreatedDateTime),3))+'_'+CONVERT(varchar,DATENAME(YEAR,OSD.CreatedDateTime)) as MonthYear

from pay.OtherSalaryComponents OSD

INNER JOIN PAY.SalaryComponents SC ON OSD.SalaryComponentId = SC.SalaryComponentId

INNER JOIN PAY.ComponentGroups CG ON SC.GroupId = CG.GroupId

where OSD.EmpId = @EmpId

) as q

UNION

SELECT * FROM(

select SD.EmpId, SD.SalaryComponentId, SC.Description,SD.Amount,CG.GroupName,

Convert(varchar(20),left(DATENAME(MONTH,SD.CreatedDateTime),3))+'_'+CONVERT(varchar,DATENAME(YEAR,SD.CreatedDateTime)) as MonthYear

from pay.SalaryDeductions SD

INNER JOIN PAY.SalaryComponents SC ON SD.SalaryComponentId = SC.SalaryComponentId

INNER JOIN PAY.ComponentGroups CG ON SC.GroupId = CG.GroupId

where SD.EmpId = @EmpId

) as q

return

END TRY

BEGIN CATCH

END CATCH

END

 

........................ 

 

The above Amount colum some months have no amount means empty itshows thats y insted of empty i wana repaced with zero plz reply fast