“触发插入后”从另一列插入数据

Question

这里我有这样的表

目的地：

  |id_dest | price |
  |     1  |2000   |
  |     2  |100    |
  |     3  |1000   |

项：

   |id_item | weight | id_dest |total(weight*destination.price) |
   |      1 |     3  |      2  |

触发器应该

   |id_item | weight | id_dest |sum(weight*destination.price) total |
   |      1 |     3  |      2  |300

查询触发器应该如何？

Answer 1

CREATE TRIGGER trigger_name 
    BEFORE INSERT ON item
    FOR EACH ROW 
BEGIN
    UPDATE item
    SET total = (SELECT d.price *, NEW.weight 
                 FROM destination d 
                 WHERE d.id_dest = NEW.id_dest)
    WHERE id_item = NEW.id_item; 
END