oracle 数据库编程范式

在oracle数据编程过程中，我们需要遵循一定得范式来保持代码的健壮性。
无论是函数还是存储过程都必须有异常处理块：

create or replace FUNCTION CMS_DPS_GETW1W2QTY 
(
  P_ITEMCODE IN VARCHAR2,
  P_YEAR_W1 IN number,
  P_WEEK_W1 IN number,
  P_YEAR_W2 IN number,
  P_WEEK_W2 IN number,
  P_HEAD_ID IN varchar2
) RETURN NUMBER AS 
total number;
BEGIN
select sum(p_qty) into total  from ifce.vw_scu_mrp_list m where 
m.source_head_id=P_HEAD_ID
and m.item_code=P_ITEMCODE and ((m.p_year=P_YEAR_W1 and m.p_week=P_WEEK_W1) or (m.p_year=P_YEAR_W2 and m.p_week=P_WEEK_W2));
  RETURN nvl(total,0);
  EXCEPTION WHEN OTHERS THEN
  RETURN 0;
END CMS_DPS_GETW1W2QTY;