How to update table automatically in MYSQL using TRIGGER

问题

I have a table in mysql database where I am calculating New Owed Balcance based on the interest + amount borrowed... I want it to be that when the interest is altered the new owed balace changes I am using Triggers but it does not seem to update it when the interest changes

DELIMITER |

CREATE TRIGGER updateloan BEFORE INSERT ON loan
  FOR EACH ROW BEGIN
    SET NEW.app_amnt_owed = NEW.app_intrst +NEW. app_ln_amnt;
  END;
|

回答1:

CREATE TRIGGER updateloan_update
  BEFORE UPDATE ON loan
  FOR EACH ROW
  SET NEW.app_amnt_owed = NEW.app_intrst + NEW.app_ln_amnt;

来源：https://stackoverflow.com/questions/9510896/how-to-update-table-automatically-in-mysql-using-trigger