Create MYSQL Trigger
MYSQL Triggers can be created in order to make an update on a database table only when a specific condition is met. With the code the code below, there are two columns in one table that can be cloned. For example, columnb can be a cloned copy of columna only when the date in the date column is in the future. Therefore, if the date is in the future for a specific entry and columna is updated; then columnb will be updated too. But, columnb will not update if the date column is in the past.
CREATE TRIGGER updatemytable BEFORE UPDATE ON tablename
FOR EACH ROW
IF NEW.columna <> OLD.columnb AND OLD.date >= now() THEN
SET NEW.columnb = NEW.columna;