MYSQL Change Values based on Table values (Constraint or Trigger?)

Question

Quick few questions on MYSQL syntax, it seems extremely hard to find these answers on google. Is it possible to set a constraint or trigger so that when a value of a column reaches a certain point it get's reset and something else is done. Or also if say hourLog is greater than zero, then licence status changes from Default value of INVALID to Valid.

I know all this could be done with a program that was using the database, but was just curious if there were MYSQL commands to do this automatically with a trigger or a Constraint.

Sorry if this was posted, I just was looking for quick clarification for a class.

Answer 1

You could use these two triggers, one for the UPDATE, one for the INSERT:

CREATE TRIGGER upd_yourtable BEFORE UPDATE ON yourtable 
FOR EACH ROW
  SET new.licenseStatus=
      CASE WHEN new.hourLog>0 THEN 'Valid' ELSE 'INVALID' END
;

CREATE TRIGGER ins_yourtable BEFORE INSERT ON yourtable 
FOR EACH ROW
  SET new.licenseStatus=
      CASE WHEN new.hourLog>0 THEN 'Valid' ELSE 'INVALID' END
;

Please see fiddle here.