Oracle PL / SQL触发器：使用where条件更新/插入

Question

Maybe it's quite easy but I don't get ahead. The table B contains two fields: product_no NUMBER and product VARCHAR2 . What the trigger should do is to insert a corresponding product description from BP-table in which you also have the fields product_no and product . Eg you enter 20 in B.product_no then it should be automatically entered the right product from BP-Table . Oracle version is 11g.

CREATE OR REPLACE TRIGGER A.trigger_on_B
AFTER INSERT OR UPDATE
ON A.B FOR EACH ROW
DECLARE
  varProduct varchar(20);
BEGIN
  SELECT bp.report_info 
    into varProduct
    from  bp, 
          B
   where bp.product_no = B.product_no;

   insert into B (product) values(varProduct) ;
exception 
  when others then NULL;
END;/

Answer 1

You can user pseudo records :new, :old, to make it work:

CREATE OR REPLACE TRIGGER A.trigger_on_B
AFTER INSERT OR UPDATE
ON A.B FOR EACH ROW
DECLARE
  varProduct varchar(20);
BEGIN
  SELECT bp.report_info 
    into varProduct
    from  bp
   where bp.product_no = :new.product_no;

   insert into B (product) values(varProduct) ;
exception 
  when others then NULL;
END;

• Get rid of the line when others then NULL; this is unappropriated you can't hide any exceptions.
• Get rid of your triggers, it is hard to maintenance code with logic in triggers. For more information check this article