declare @system_status varchar(30)
select @system_status = '12,20'

declare @sql nvarchar(4000)


select @sql = 'SELECT [system_status] 
FROM VW_Document_Main 
WHERE 1=1 ' 

IF @system_status IS NOT NULL AND @system_status NOT IN ('-1','0') 
BEGIN 
SELECT @sql = @sql + 'and ('','+@system_Status+','') LIKE ''%,''+system_Status+'',%''' 
END

PRINT @SQL