SQL SERVER SP select 条件where加变量

存储过程中select 　where条件后如果条件关联变量则可以使用如下代码，变量允许为空，当为空时则不会执行筛选条件　

Select Distinct TR.int_id, TR.vch_pmd  from  table_r   TR 
inner join TABLE_PPT  on TPPT.int_id = TR.int_id 
where   (TPPT.vch_s_code = @in_Code or len(isnull(@in_Code, '')) = 0)